Pociwo It's irrelevant if app is on F-Froid or Play Store if it's FOSS. Play Store is more secure tho. F-Droid only seems to care about apps being FOSS but they don't seem to care about security.
That's actually untrue.
F-Droid provides an exact source code archive for the compiled binaries, so you know exactly what is in them. From google store on the other hand, it may be fundamentally an open source program, and they may even link to a source code repository, but you don't have any way of knowing exactly what was used to build it, you can't tell what revision was built, and you can't tell if they slipped in some dangerous extras.
Google does NOT audit the security of applications it hosts, could be absolutely anything going on. You have no way to know.