Has had Musl for awhile here is the install stage www.gentoo.org/downloads/#amd64-advanced . Bunch of docs on their wiki too. Gentoo is a rolling release you are correct but there is testing and stable branches. Stable branch is enterprise production ready. I know of a few hardware vendors that are using a custom gentoo builds under the hood. One of them is a big name storage array company that people spend hundreds if not millions on their arrays.
My experience with Void was hyper rolling release . You get things quickly kind of like Arch.
Gentoo stable runs a little bit older software for stability sake. With that being said you can mix and match stable with testing. I would assume there is some gotchas but I have not run into any yet. I am running the testing branch just for KDE software right now to have the latest and greatest KDE but a super stable base.
Definitely something to take a look at if you’re a more advanced user. I am coming back to Gentoo after about 15 years off and just loving it. Compile times are not that bad with new hardware. My Intel NUC I am running on is crushing it. I remember X taking like a week to compile back in like 2003 lol