My Oppo 203 is not MQA capable, so I always let Roon do the decoding from 48kHz to 96kHz, etc. I’ve always thought I could hear the difference, but I don’t really know for sure. I let Roon do the MQA decoding even when using my MQA DACs. I don’t see any reason not to.
The MQA DAC’s do the full render, so the 1st unfold on Roon and then the render on the DAC’s. Yeah, I don’t see a downside unless the 1st unfold is expecting or wanting to the render to take place somewhere down the line. I guess why do the 1st unfold if it’s not a benefit, I assume roon does do it because it is a beneift.
Without getting into any opinions about MQA, it certainly won’t hurt anything or degrade the quality from the non-unfolded file. Whether or not the first unfold will sound better is up to you. If you like it better then use it and don’t worry about it
MQA DACs come in two varieties: those that do the full decode - ie Roon does not do anything with MQA, and those that render, meaning the source needs to unfold the MQA stream, and the DAC simply chooses from one of the updsampling filters (32?). The differences in these filters are just tweaks in the upsampling parameters.