Securing NM wiring on the electrical panel back board - Multi-cable staple
Those multi cable clamps are listed so they can be used I have used the 2 slot 4 cable a few times without issues from inspectors, the only issue with more than 4 they may call it bundling but the listing info shows 8 so it should be ok.
You will need a clamp entering / leaving the service panel some are listed for 2 cables I don’t know of any listed for more than 2, I love the plastic “insider” brand clamps they snap in pull the cable in and are done no screws or locknuts to mess with.
If you are talking about exposed romex we usually put a nipple in to protect the cables to a height of 8’ coming out of a nipple you do need to clamp or staple the cable as it comes out not inside.  I think that hit your questions.