Neither is a must to clamp. But, a girth band from LGhanger does make clamping alot easier on the base shaft skin. When I started clamping, I didn’t use anything under the clamp. Sometimes you can pinch some skin, fairly painful. I bought the girth bands, and now I can use two clamps at once, pain free.
As far as cock rings, definitely not needed to clamp. But, a must have to keep post workout expansion. I’m a hardcore CR user! It gives me an extra.125”-.25” extra girth during sex. And, after every workout, it keeps everything expanded, for a longer period of time.
Hope this helps. I did want to mention to both of you, don’t start clamping until your dick is conditioned! You have to complete the newbie routine, or something similar, to condition your dick. If you don’t, you will injure yourself. The only injuries I’ve ever had during my PE career, came from clamping too soon.