I think there are two holes in the lock ring but you could add more if you needed to.
I generally use mine with ER collets though so yes, just undo the nut as usual to remove the part.
The main use of these blocks for me though so far has been for example to produce a hex on the end of a round bar so I remove the block from the vice to cut each flat anyway.
If you need to machine multiple parts without moving the block a 5C block like this one may suit, it has a quick release lever and of course you can get square, hex and blank collets for it. You could of course use ER32 collets in it as well with an adaptor.
