Not an iPhone guy But with Android, if linked to Facebook, no, you won't lose points. Account info lives in Facebook, - i assume it's same with iPhone
I think I once uninstalled and reinstalled the app on my iPhone. No issues. Maybe install and log into one of its sister apps (MyVegas, pop slots, etc) so that you know your LP balances and level are still active as a precautionary measure. If you’ve never logged in with your Apple ID, then you should do that. I think the balances will vanish if they’re not tied to an Apple ID.