Sorry if I am going to sound harsh but consumer's misconception that if equipment deliver louder volume with smaller turn of volume knob it must be more powerful hurt this industry.
Amp design can use linear potentiometer (bad idea), or logarithmic one (typical), and their rate of resistance change per 1 extra degree of turn can be different, and circuit can be designed in different way to allow different rate of volume increase. Ideally, one wants to have whole available '10 hours' volume span to be able to adjust volume in even way ('even' to human hearing which is logarithmic in nature), because that gives most precision in volume adjustments. Because eventually manufacturers got tired of explaining consumers that their gear is not broken if they needed to turn volume above 12 o'clock, most started to produce amplifiers where most of the volume change is happening between 8am and 1pm, and above that, volume changes a little.That is undoubtedly bad user experience, but paradoxically, that is experience that generated least amount of trouble for manufacturers.
In other words, H10 can deliver less volume for given potentiometer position compared to Magni, and that is OK, it ain't broken.
As for your comment on treble quantity, no surprise here, Schiit is known for relatively bright sound, and H10 is known for a very relaxed, "tube-like" sound, at least in its stock form.
And for gain, use whatever sounds and feels best for you, and ignore what others say, including what I wrote here
Trust your own ears, and do not let anybody else tell you what is right.