You definitely want a server to go along with the Waves card.
Going over regular USB causes way too much latency, and on top of that you are at risk of software/computer going down which will completely eliminate your audio stream.
With the server, if the software (Multirack SoundGrid) crashes, audio will continue on with the server hosting the streams.
Also, with a server, you can bring your latency down to 0.8ms, which is possible to mix IEM’s with.
I have zero experience with the SQ series and a SoundGrid network as it isn’t out to the public yet, but from my previous experiences on SoundGrid networks, it’s basically a “don’t leave home without it” scenario.