Pretty much everything is PCM. If you’ve never heard of DSD, you don’t need that capability. Even if you have, I’d say it’s of dubious worth. It’s essentially just a left-over frill from Sony trying to sell a new format 20 years ago. There are lots of threads on this forum discussing it, though relatively few discussing its actual utility.
Of course, I also think that external DACs like the ones you mention are essentially fetish objects these days, as the state of the practice has gotten to be so good.
Almost all DACs these days that support USB input use “USB Audio Class 2” interface protocols, which are supported by Linux (and ROCK).