Most importantly: plan for remappable controls from the start.
Different games use different conventions, and different players have different preferences. This is also important for accessibility - not everyone plays with the same hardware - electrically or biologically speaking - and the ability to remap controls can turn an impossible game into a ...
There are a couple setups that have become ubiquitous. Here are some common uses (non-exhaustive list):
Left stick for Player movement
Right Stick for Camera movement
Cycles zoom levels
Centers the camera on the player
Simpler approach is to set "Stretch Mode" (in project settings under Display -> Window -> Stretch) to "Viewport".
With "Stretch Mode" set to "Viewport", the rendered resolution will match the design resolution (in project settings, under Display -> Window -> Size). This may result in enlarged "pixels&...
Since you do not need to reset the scene, all you need to do is
Save the transform of the last checkpoint when you reach it.
Destroy the current player.
Instantiate the current player around the saved transform.
Move the camera back to the player if it not done already.