I used the bottle until recently doing manual. My problem with the Evo is less the function of the ATO and more the variation in chamber levels depending on how much gunk gets in the floss in chamber 1. By the end of the day, the "steady-state" water levels in chambers 2 and 3 are lower than at the beginning, likelydue to increased flow resistance, so the ATO overfills and salinity drops a bit--over a few days water level in the tank rises and the salinity is lower...
For OP, if you don't have a problem with your chamber levels (aside from evaporation), the gravity bottle works just fine.
That said, I missed a day and a half of manual topup (covid) and now my urchin is on the way out :-( might be best to go with something even if imperfect.