There shouldn't be any audible difference in the Blackhole plug-in between the different resolutions of your DAW. Theoretically, running at the highest sample rate/bit depth is most "ideal", but the fact is that (arguably) won't change how you hear the reverb tails. Blackhole doesn't generate any log files regarding its performance, and unfortunately in the plug-in world we are at the mercy of the DAWs processing schedule – but as long as the audio is being rendered in the allotted time, no problem.
I think the issue you are mostly running into likely has to do with the settings in the plug-in itself. If Gravity is set very low (near 0 on the positive side), you'll have a very dense decay, which might sound muddy. If the Low and High EQ settings are set in a certain manner, it might sound muddy. If you have Feedback up and Modulation down, the build up might cause a muddy sound. Etc Etc. Keep in mind that Blackhole isn't primarily intended to be a clean, natural sounding reverb, but rather other-worldy. That being said, does it always sound muddy to you, no matter the setting?