I would be quite open for any kind of isekai. Both Medieval European Fantasy like in Japanese mangas or Far Eastern Martial Arts realms like in Chinese manhuas would be fine with me. Steampunk style would also be interesting, as would something completely unusual, like Hittite Ancient Near East for example. Generally I would prefer a world with legendary creatures compared to one without. But they aren't necessarily a must if there are other interesting organism to encounter befriend, e.g. dinosaurs. Magic would also be interesting to have.
Regarding the topic as what I would be reincarnated, I would likely prefer humanoids of any kind compared to anything amorphous like a slime or any creepy-crawlies (my phobia against the latter hopefully gone in my new life). Being some kind of powerful monster with anmal shape is also a possibility. I could even imagine being reincarnated as a kemonomimi. Why aren't there any main characters reincarnated with animal ears in mangas, manhwas or manhuas, by the way? I understand that it must be nice to fluff them but wouldn't it be nice to have some myself as well, the more so as animal senses are undoubtingly superior? I believe good health and sufficient sustenance to be important which doesn't necessarily mean that I have to be nobility or anything equivalent. Being reborn with my current gender would be nice but I would also be open to live my next life with another gender.
What I would definitely be against is being transported to isekai in my reconstructed own body, even if it is a younger version of myself. About why, just imagine how a wheelchair isekai most likely would work out (here shown at the example of a Medieval European Fantasy). You wake up in a forest sitting in your wheelchair only to find tree roots and uneven terrain all around, not to mention all the monsters you can't even really run away from. Well, perhaps your wheelchair can now fly but in my case I have a fear of heights which leads to new problems. When you then manage to exit the forest and you find a road, it most likely is made of cobblestone if not even worse. For all who don't know, cobblestone is something like the natural enemy for the little front wheels of wheelchairs. And when or if you finally reach a town they likely don't let you in in the first place because you are a "useless cripple" - a very Medieval way of thinking indeed. If you are allowed inside of the city walls you will likely find stairs in front of almost every shop thus denying you entry. Not to mention you additionally have likely some potentially lethal illness that requires lifelong treatment easily avaliable in the modern world. The medicine you need every single day either dosen't even exist or is so expensive that you can't afford it anyways. Not to mention that you can't get a job because not even the adventurer's guild would take you. Well then, good riddance!
Therefore I would prefer to be reborn rather than just being sent over. Finding myself suddenly in isekai with a healthy body I never had would also invite problems since I don't know how a healthy person would use it's body, do I? Thus I would prefer learning everything anew from infant on. If that is possible: Isekai, here I come!