It is one partition at a time with capture to wim.

Depends what you are doing. If you just want to restore the os partition, the existing esp partition stays as it is and is fine.

If for whatver reason you want to replace the contents of the esp it is very easy.

one simple command

bcdboot <windowspartition>

e.g.

bcdboot c:\windows

that will automatically find the esp if there is only one.

If you have several disks and esp partitions you specify the target esp with the /s switch

e.g.

bcdboot c:\windows /s z:

or

bcdboot c:\windows /s \Device\HarddiskVolume1