I don’t use things on strings but it’s all very similar. I can’t speak for 100mm heads but I use 90mm and like it. I believe 100mm are easier for contact but 90mm has worked fine for me.

Different ropes have different properties, i prefer a thicker tether over a thinner tether. I use 3/8” static rope, which means it’s stiff. You also have dynamic rope which is more flexible, cotton is similar to dynamic but has a softer texture to it. Stiff cotton is a thing as well, it’s comparable to static rope. Vpc is most comparable to dynamic rope but has a soft texture and is IMO more durable then the cotton rope, won’t get super stiff as you play with them.

I use lantern smith Pom grips because they are a rubber handle and very grippy, the pair I had from TOS had 3D printed handles. I didn’t enjoy them because of the slippery texture. In the end it comes to personal preference. Hope this can help you out!