The D90 is effectively indistinguishable from the RME ADI-2 DAC FS. You pay less since it is just a DAC. If you only need a DAC, it’s a viable option.
If you didn’t enjoy the original Gungnir MB then, unless you were using it via its single ended outputs, you probably won’t enjoy the Bifrost 2 either.
Topping’s DAC/amp offerings have (to date) pointlessly high output impedance so they’re only suitable to use in that form with higher impedance headphones. But you an just buy a DAC-only version with a proper amplifier.
I’ve no issue with the D90. The D70 was fine, but a bit pointless given the existence of the D90. The D50S is okay if you run it with lossless content - but I’d pass on it entirely for use with Spotify (specifically) unless you’re okay with running it at - 3 dBFS. It’s not my thing, but it is technically competent.
The D90 is the only Topping DAC I would personally consider, but I’d rather have the RME.
The ONLY DACs I would bother with for use with HQPlayer would be TRUE NOS DACS. And of those you mention, that is ONLY the Holo Audio stuff. Otherwise they are ALL applying their own oversampling, noise shaping and filtering (NOS mode on the RME is NOT true NOS).