I've never used a spreadsheet for my army.
Exarch powers are not psyker powers or anything that gets "activated" mid-game. Instead, they are selected during army creation. In this regard they work a lot more like wargear than they do like psyker powers. Also, for most Exarch powers there's just a single one that's obviously the best and so you always take it (like hawkeye for Crimson Hunter Exarchs) on every unit. I would say in terms of decision-making I consider them similar to wargear options. No concerns about that.
Eldar tends to cast more spells than other armies, though. Generally speaking, I make little tokens for each spell so I know what I've cast each turn, and I put them next to the unit I've cast them on. Usually they are pieces of card paper or cardboard with the spell's name on it. Here's what an example psychic phase looks like for the army I'm running these days with my 2,000 point army:
- Hemlock Wraithfighter casts Jinx or Smite
- Spiritseer casts Ghostwalk or Protect/Jinx
- Warlock casts Focus Will or Protect/Jinx
- Farseer casts Doom, then Farseer casts Fortune
Unlike Thousand Sons, which will regularly be casting north of 10 spells per turn, almost all of which are unique, Eldar lists will usually cast 3-5 spells per turn. You can definitely choose to make an Eldar army that casts 10 spells per turn, but we don't have as many good smite-like spells as Thousand Sons, nor do we have any abilities that offset the Psychic Focus rule so we can't spam smite. As a result, Eldar psykery tends to cap out pretty low.
IMO, Eldar is a finesse-heavy faction to play with more decisions to make than many factions, but in terms of complexity of psychic phase or need for spreadsheets I would not consider it comparable at all to Thousand Sons.
That being said, if you want a complete break from psyker powers, Eldar isn't the faction for you. Every Eldar army always includes at least 1-2 psykers. You bring a Farseer to cast Doom if nothing else, and some of our spells, like Doom and Jinx, are very crucial to making the faction work.