Oh, I've answered a fairly similar question before. I still like that answer so I'll link it in the bsky post. Buuuuuut as for the specifics of tentacle design, generally I prefer them simple! The ideal is a goo tentacle that can stretch things out but still be squeezed into tight spaces but I'm also partial to just a thick rounded tube like a Nihilego. I've spent too long staring and being mildly disconcerted by the Octopi in the F.I.R.E. aquarium to want those creepy suction cups anywhere near me. On the perfect other end of the spectrum, if any of you happen to have Doc Ock arms feel free to do whatever you want to me with them!