Sorry for the late reply.
So I tried it again, but now with the gog installs. I copied the files from a PC and it works
MM3 is fast as it can be, now low fps loading screens.
Ultima 6 has sound and no stuttering. (I tested this one too from a random dos rom download and was bad, stuttering and without sound)
So I’m not sure what changed but from GOG everything seem to be working flawlessly.
Thanks for the help.