I tried the one with the most downloads and it worked fine on my Optimus 2. I did encounter a barrage of ads while setting it up (custom menus), but in day to day use I did not encounter ads.
I am now trying the one marked as ‘New’ on my LEM 12Pro and while from the same developer is a little different in the way you customize. Ads are rampant during setup but using actual button day to day, I’ve not run into ads.
While both of these are from the same developer, the first one is subscription based and the second one (New) is a one time fee. Both have been updated in August 2021. I think continued development is important and I do believe in supporting developers. Neither has presented any issues to date on either watch.
I own Smart Touch Pro and it has been pretty solid operationally on both watches. I do find the print to be small for my old eyes and the favorites menu doesn’t scroll and therefore I’m limited to 6 favorites. Maybe the screen size limits the number of favorites. The biggest concern for me is that it is no longer supported.