Hey errrbody!!!

I'm banging out a couple "showcase" mobile apps for practice, portfolio, and/or as potential templating tools.

I have no issue writing the code, I just wanted to see if I could get a couple pointers as far as user databases go. I'd like to have some "user profile" features generated from a FB...vlike profile images, name, address, contact, yadda yadda yadda. I usually use Firebase, but I am still having a little trouble with the more advanced stuff when it comes to integrating users profile data. I can get values from Google and whatnot, but I'd like to see what my other options are on the smaller scale.

I am currently writing code in Flutter/Dart, ReactJS( not native!), Vanilla Js, Python, and CPP.

I know there's options for client side storage like Shared Prefs, Sqflite, etc, as well as server/DB side stuff like Firebase, Aws, Mongo, Node, SQL, etc- you get the idea.
I just want something with decent documentation that's reliable, not a massive undertaking (at least not for all this little stuff, anyways) and could potentially be a go-to platform configuration in the future. It'd be cool to wire in my Flutter and js shit of possible, bit honestly I'm cool with having separate setups for the time being. Any extra input regarding the use of python and/or cpp as well (either separately or with mobile) would be rad as fuck!!!
I do realize it's a pretty vast area to cover, but I figured it couldn't hurt to see what everyone likes to use for full-stack setups.
Thanks!!!!