40 (max) and 35 at the least, but then I’d say to level them up to 40 once you go up to th11 (and focus on any other things)
I would. Sneakies alone are probably 4x more efficient than anything you can scrape together at TH10. As an example, I regularly and easily farmed 80k+ dark elixir per hour as a TH11/12 without boosting barracks or losing trophies.
Put 1 on cc (very important), keep 1-2 builders on army camps, 1 on warden at all times (aim to get it to lvl 5 before cwl starts), 1 builder for the new buildings that get unlocked when you reach th11, 1 builder on queen if you have enough DE. Then dragons, bowlers, freeze spell and bat spell would be ideal (Depending what strategy you want to
. 365 400 137 291 163 444 245 334

coc when to upgrade to th11