all these ideas sound really cool to implement! for each:
garden of the gods- lots of statue fountains and white carnations / flowers?? overall, go for a very white theme, with villagers who are white (too bad none of the villager houses are white), like blanche, diana, bianca, rolf, ruby, whitney, felicity, daisy, tia etc. character houses could be shrines!! use music boxes and zodiac stuff!
baker paradise: character houses are, of course, eateries! but try to make them each a lil different- one can be the cliche sit-down bakery, one can be a cake shop, one can be an artisan's working place, etc. in town, everything would probably be more woodsy, but leave easter eggs around? pink flowers! use food themed villagers like tangy, tia, merengue (ofc), zucker, mint, chai, etc.
overgrown library: tbh i like this idea the most! lots of cedars, each character house is woodsy and ofc filled with books (but make one a library and one a bookworm's house). use the fireplace and rocking chair a lot! leave the book lost item all over the town (and i mean alllll over), and use the log bench pwp, as well as other wooden pwps. misc flowers to make the town look less structured
i know you asked for opinions on which theme is the best, but i couldn't hold myself back from spewing ideas oops. like i said, i like the overgrown library one the best, but i hope any / all of the ideas i gave you for any of the three themes help you some!! good luck with choosing a theme- these are all really creative!