If the tablet has LTE (mobile data) then go to airplane mode before you fly. It's also important to make sure all background apps (especially DJI Go 4) are closed so the background is clear.
I would keep Litchi as default so when you plug the tablet into a Connected controller, it starts Litchi straight away.
If you lose app connection in the air (either Disconnected or Signal Lost), see if the aircraft still responds to controls. If not, go to Sport mode and try again - that usually works IF the controller is still connected, but the app has crashed. If you have control, fly it back visually and land. If you aren't visual, or don't have control, press RTH once (for at least 5 secs). That should get it coming back by itself.
If you cant see the aircraft, and don't know if its coming back, turn controller off, disco the tablet, then turn controller on then reconnect. That should bring it all back.
The only very important thing to remember is that if you press RTH multiple times it turns it on and off - so do it once.
I am considering getting a tablet to avoid using my phone. However, Samsungs suffer from bloatware. If yours is out of warranty, consider rooting it to uninstall apps you dont want and free up precious RAM.