1. This relying on rcm mode and me being on 5.1 once i install cfw could I update the switch firmware and keep cfw with no problems? Even if by that means waiting for the cfw to be updated for the new firmware version.
You will always be able to use RCM to load CFW, so you don't need to worry about updates preventing you from loading RCM payloads.
The way ReiNX works, updates to the Nintendo Switch shouldn't, in principle, cause ReiNX to stop working, but you should always check ReiNX compatibility before updating your Switch. Worst case scenario, ReiNX will need an update to be compatible with a newer Switch software version.
2. Is stuff such as rcm tinfoil and jig burning efuses? Because I really don’t understand what the whole deal with Efuses is I looked wiki but can’t quite understand. What do you mean burn? Is my switch dead once I burn too many efuses or what? :s Seems to be mainly about downgrading?
Each time you install an update to your Switch, efuses are burnt. This is to prevent downgrading. For example, if you try downgrading your system, but there are too many burnt efuses, the Switch will refuse to boot without CFW.
If you care about being able to downgrade in the future, you should
update without burning efuses. If you don't care about preserving the ability to downgrade, then you don't need to worry about efuses.
1) You should be fine with updating your system firmware alongside using the currently released CFW (e.g SX OS. Atmosphere & ReiNX will be the same).
My understanding is ReiNX and SX OS function in a way that makes them mostly futureproof. However, in its current state, Atmosphere would likely require an update before being compatible with a future Switch software version.