First of all, after doing some further comparisons, I'm starting to lean on either using HQP or PGGB for upsampling and then adding crossfeed and noise shaping in HQP. Combined upsampling gives ok results, but the challenge seems to be that sound becomes one-size-fits-nobody. PGGB aims respect the original recording more religiously, while HQP makes it something different. If one wants absolute transparency, pure PGGB is the way to go. If one wants to go to movie theater, HQP is the tool. I wouldn't say that the biggest difference is in warmth, but more in spacial representation. HQP is much grander, bigger, "impressive". That works very nicely with very many genres. However, with jazz/classical/acoustic, HQP compromises timbre and transients as it kind of opens up everything.Did you hear any loss of warmth when processing with PGGB at 1536/ 768?
If I opt HQP for PCM to DSD upsampling, which filter and modulator would be appropriate to compete with PGGB?
I haven't fiddled too much with DSD. I'm currently running HQPE in WSL and I lose so much processing power that I can't run many modulators at high rates. Would need to study further how to enable lowlatency kernels within WSL. GoldenOne's measurements seemed to point that -super 512+fs has amazing measurements and I would guess that it's the best modulator for PGGB files. However, to my ears, PGGB sounded better on PCM.
I'm still going through the process of figuring out how I will setup everything. I clearly prefer PGGB with jazz/classical, but for other genres HQP upsampling seems to give me better results. I think I'm going to mainly use just Roon+HQP for most of my listening, but then build collection of PGGB'd acoustic music that I occasionally visit for critical listening.