[...] If I have, some BTC coins already in the wallet and then I remove it to make a space for another one. Do I lose those coins? Is all BTC data wiped out? What happens if I remove other wallet and reinstall BTC? Would I my coins be still showing up? [...]
You don't loose anything. you can delete all the apps and reinstall them anytime without lose nothing. your coins will be always there. the most important of the wallet is keep safe the seed.
[...]
As far as i know the ledger team is working on an app handling all currencies. [...]
That would be the perfect system. only 1 app that handle all the coins. something like exodus.io