Questions to "490 Electronic Circuits/second"

Blueprint: https://pastebin.com/TDHncw9K

in my approach to build my very first mega base I try to plan out sub factories for green circuits, steel, gears, plastic, ...
The build runs well with 2 trains for each item (3-6-0)(iron ore/copper ore/green circuits) and around 3600 logistic robots.
This is the first time, I use robots in this scale.
So after designing this I got a few questions:
- should I take smaller trains to transport the green circuits (since they are needed at several different other spots elsewhere)?
more little portions instead of fewer big portions?
- should I take bigger trains for the ore input? (4-8-0)?
- is it a good way to go (in general) to input raw resources to get a specific intermediate product? (or central smeltery area -> subfactories)?
- I see many robots hovering around the roboports/ontop of the requester chests. Is this because of the lack of roboports or is it normal?
- is it possible (with circuit network) to prevent uneven unloading of the ore provider chests (at the top)by bots? the second wagon W2 (loc1-loc2-loc3-W1-W2-W3-W4-W5-W6) is always the last which gets emptied and I thought this might result in troughput problems?!
- is the train signaling right (esp in the upper half) to prevent traffic jams when I add additional train(s)?
- any suggestions to improve performance/UPS?

I am excited kinda and can't wait for your thoughts on this thing :)
regards, raneo