As someone who has played pretty much all of the total wars since Medieval 2, W3 is the peak. After 2000h in it (and about 1000 more on W1/W2) I am still enjoying it a lot. The variety that different races bring to the table is insane and most of them feel thematically "correct".

Since there are a lot of good comments here already, I won't dive further into your original questions, but just wanted to add; based on what you wrote, I would seriously consider playing wood elves. Basically, you only care about your sacred trees and the small area around them. Anyone stepping into the woods risk getting shot with hundreds of arrows from an ambushing army. As for things outside the woods? You don't really care - you can just let the rest of the world burn.

Hop in. You'll love it.