torrenting works just fine, I don't do it much though. soulseek is my main jam and it's only pretty good, mullvad allows you to open up ports but you don't have any control over which ports they give you, so you can't get the two consecutive ports soulseek wants opened, only one. Still works but I have issues trying to browse other people's files.
The connection quality is NOT as good as PIA, I think they're skimping on their peering. I get good performance within my country or to close-by regions, but if I try to choose a far away country or cross an ocean for extra FUCK GLOWNIGS to make it harder on them then I get a shitty connection. had to switch to TCP because it was shitting up lots of applications that don't deal well with tons of loss and out-of-order packets (default UDP).
One of the main draws of mullvad is that you can literally send them cash in an envelope with your account details, so it's supposed to be better than paying with a pozzed credit card or bitcoin etc address that is almost certainly linked to your meatspace identity. I haven't done it yet though since they said they were experiencing mail delays from the chong virus.