Humans versus Tron

Early:

    On the play most Tron nut draws are good enough, and on the draw Tron probably needs a turn four sweeper.
    Humans' disruption is best if it can stop the assembly of Tron as there are so many threats that do something.
    Humans functions best here when it has a strong clock with enough disruption, not a bunch of slow lock pieces.

Mid to Late:

    Tron activates an Oblivion Stone or Ugin, the Spirit Dragon and wins if the game gets here.

Technical Details:

    If Humans is going after Tron's threats with disruption it should do some clock math. If it costs more than a turn of Humans' clock to disrupt them, going for the fast kill is likely better. If it costs exactly a turn, have fun with that judgment call.
    If Tron is on the draw with an Urza land and a Chromatic Star effect, Humans might just want to Meddling Mage Sylvan Scrying.

Sideboarding:

    Tron must worry about Damping Sphere. Hedging with some Nature's Claims is low cost as it still hits Aether Vial, and killing a Chromatic Star to gain four life can save it from a turn four death in spots.
    If Tron runs out Oblivion Stone without activation mana it can get Reclamation Sage'd, but that is a narrow concern.
    Thragtusk is fine but unexciting for Tron. The Beast doesn't win the runaway games Tron loses.

Overall:

Tron was solidly ahead before Dominaria. It is still ahead but lost enough percentage points in sideboarded games to make me worry that Humans is no longer a reason to play the deck.

Humans versus Blue Control

Early:

    Humans is trying to clock Blue Control under a sweeper. Blue Control has enough other answers to make the usual disruption merely temporary. Humans wants to present a clock and pepper in disruption at the most inopportune times, but often it must hope to fade a sweeper.

Mid to Late:

    If given any window, the Blue Control deck is going to stick a planeswalker and win the game. Slow threat deployment from Humans doesn't work against Teferi, Hero of Dominaria and Jace, the Mind Sculptor.

Technical Details:

    Early Meddling Mages are often better off trying to hit Snapcaster Mage or cheap removal as the sweepers have too many names these days.
    Draw step Aether Vial activations lets Kitesail Freebooter and Meddling Mage cover Terminus in response to the Miracle trigger.

Sideboarding:

    The big swing here is Humans gaining Sin Collector. I suggest you watch Game 3 of the SCG Tour® Minneapolis Finals from May here . If Sin Collector dies, the Control player is still down a card which means their sweeper doesn't also open up multiple other cards.
    Blue Control wants to cut all the counter magic. One of the little "gotchas" is that Celestial Purge is good as it covers all the discard creatures to prevent Phantasmal Image-ry and Mantis Rider.

Overall:

Things are even worse than they were in the Tron matchup. Blue Control is a heavy favorite here.

Humans versus Mardu Pyromancer

Early:

    Mardu can lose games early if it doesn't do enough things for one mana. It doesn't have reset buttons, so hands of Lingering Souls will be chump blocking giant Humans and dying.
    Conversely, Thalia, Guardian of Thraben is Humans' best hope of running away with a game. Making their one mana stuff cost two then overrunning them is good stuff.
    Champion of the Parish isn't the best one-drop. Making multiple plays a turn via Noble Hierarch is how you get ahead of the cheap removal, and Champion not dying early is often a sign anything would have killed them.
    Young Pyromancer can run away with a game if Mardu gets to establish it early. Humans has Reflector Mage to briefly stall it, which makes multiple Pyromancers a liability.

Mid to Late:

    At the start of the mid-game, if Humans is ahead it can stay ahead and can close, if it is behind Mardu can just keep pace turn for turn and win.
    Mardu has an easy win button of keeping the battlefield clear and slamming a Blood Moon at the start of the mid-game. This turns Humans being behind into a clean-cut win.
    Given parity, mana flood often decides the game. That means Mardu needs to maximize Faithless Lootings, holding extra lands and only filtering less than two dead cards if really needed.
    One way Humans has to get back into a losing game is Phantasmal Image on Bedlam Reveler. Phantasmal Images should be saved for worthy targets, and Mardu casting Bedlam Reveler without a discard-cleared path is a definite risk.

Technical Details:

    Just watch the Gerry Thompson versus Javier Dominguez match from Pro Tour Rivals of Ixalan, there two master class players battling this out.
    Humans wants to hold extra lands and Aether Vials in hand to protect topdecks from Kolaghan's Command discard.
    Meddling Mage should choke Mardu's assumed next on-curve play or just aim for their best answer of Lightning Bolt.

Sideboarding:

    Humans wants to bring in too many three-drops. Izzet Staticaster is key to managing tokens, and I think Humans must hedge for Ensnaring Bridge with Reclamation Sage, and Sin Collector is a must-have. I think this means they shave on Reflector Mage and weak two-drops like Meddling Mage.
    Auriok Champion is nice for Humans to have and gives it a long-term advantage. Mardu really needs Engineered Explosives or a similar out to the card these days.
    Mardu wants to trim cards that get punished by Thalia, like Manamorphose, or discard that is bad to topdeck.

Overall:

Mardu is ahead by default, but Humans has a clear route to wins. Get ahead on tempo, pressure hard, and don't flood.

Humans versus Ironworks

Early:

    Anything short of the Humans' disruption hardlock is fragile, with the hardlocks being three Meddling Mages set to Krark-Clan Ironworks, Engineered Explosives, and Pyrite Spellbomb or two non-Image Mages that you then boost to 3/3s to dodge a Pyrite Spellbomb.
    Thalia, Guardian of Thraben is a bit of a bust against Ironworks fast mana and the fact Engineered Explosives counts the extra payment for sunburst, making Explosives for two counters still cost two mana.
    As with Tron, Humans wants a good clock with some disruption.

Mid to Late:

    Ironworks needs to be careful about deploying Scrap Trawler as a chump blocker as getting it Reflector Mage'd is a Time Walk problem. Myr Retriever infinite loops are easier to live without as a couple Engineered Explosives activations is enough to safely pass turns and kill later.

Technical Details:

    Humans curves that produce lethal threats that cost one or three alongside hate are slightly better as those don't die to Engineered Explosives.

Sideboarding:

    Humans has no hope of a hardlock against Ironworks' sideboarded red removal. Even Kambal, Consul of Allocation or Kataki, War's Wage just dies. Keep hands that are clocks with some disruption, not slower ones.
    Damping Sphere exists but dies to Engineered Explosives. From the Ironworks side I wouldn't worry too much about having Nature's Claim.

Overall:

I would rather be on the Ironworks side of this, which explains the recent success of that deck.

Humans versus Hollow One

Early:

    Hollow One's best draws produce multiple very early 4/4s or 5/5s. The goal is to clock Humans as fast as possible with multiple things they have to chump block. Multiple forced chump blocks eventually break parity and it's Reflector Mage proof.
    Humans wants to rapidly grow a creature to 6/6 so it can block anything. If the game goes longer, Humans overwhelms Hollow One. If Hollow One has removal, it should aim it at things that can grow.
    Phantasmal Image copying a big Hollow One creature forces a removal spell and is big a problem.

Mid to Late:

    A turning point against slower Hollow One hands is if Humans gets to double block something profitably. This often is the result of Reflector Mage's 2/3 body after an attack slow down.
    Hollow One's plan in longer games is to close with Flamewake Phoenixes and burn. This makes Mantis Rider important for Humans, allowing them to stymie these chip shot attacks.

Technical Details:

    Adding a +1/+1 counter to Kitesail Freebooter also makes it an effective blocker for a 2/2 flier.
    Fatal Push can target a Phantasmal Image acting as one of Hollow One's high drops.

Sideboarding:

    Humans gains Reclamation Sage to stop Hollow One's fast draws. Multiple delve creatures still get bricked by Reflector Mage, and now Hollow Ones permanently disappear.
    Hollow One gets Grim Lavamancer and Engineered Explosives. Simple recursive threats with this great interaction can take games that would be unwinnable for the base Hollow One configuration.

Overall:

Humans has too many tools that mess up Hollow One's progression. Their best draws are good enough, but sometimes just barely.