FSN Ultimate Edition settings

Important Options Settings:
Display - Quality - High
Make sure to play in 3:4 and not widescreen. Widescreen crops CGs to fit. Some work, others don't. Not recommended. (This has apparently been patched but unless you really hate 3:4 still recommend not using it)
Patch - Textual content - Mixed
Patch - Music content - Mixed
Patch - Censor - Un/Decensor H content (Make sure this or censor H content are the only checked box. Details below)
Rin chant language - Japanese

The following should also be the only checked boxes.
Voice - Play Unmatched Voices, Play Unused Voices, Use custom Wait-Voice tags, Use custom voice replay icons, Don't stop currently playing voice when clicking
Vita additions - Vita Movie Menu, Vita About Menu (Do not watch these movies unless you've finished the route. They contain massive spoilers)
Gallery - Extended gallery, Merged gallery, High quality thumbnails
Options - Display scene title in history, Disable forced auto-read, Skip movies in-game

Feel free to play around with other settings, like font and scroll speed, etc. Whatever makes it more convenient/enjoyable for you is fine.

Sexual (H) Content Info:
For the first two routes, you can and maybe should play with them off, aka Censor H content. They're not good, they don't add anything, they outright detract from the routes.
However, the third route is a special case. The scenes themselves are still hilariously awful, however their presence is thematically important to the route and the character they pertain to.
To make them not happen, the narrative bends itself over to introduce new, strange aspects, and in doing so muddles the message of the character quite a bit.
This is why it is recommended they are on for, at the very least, Heaven's Feel (Third Route).
However, if you genuinely just don't want to have to deal with gut-bustingly awful smut, just the knowledge that anything to do with (highlight to reveal spoiler) vampire stuff is there to replace the characters having sex should be satisfactory.
(For reference, uncensor H content makes the H scenes happen, decensor is a fan-made art filter that removes the pixelation of the art screens, and censor removes the H-scenes entirely. If you have them uncensored or decensored, do not read this in public/around other people lol)

Last Details:
Finally, within the in-game Config menu (open by right clicking the screen), click "BGM". Make everything Remix, then swap the songs Emiya and The End of Reminiscence back to the original.