I think it’s just a problem that comes when using multi-effects-pedals / modellers. People keep asking for unity gain across presets/programs on every forum whatever the device. And understandably so. It would make things a lot easier. But it simply doesn’t work like that, because different sounds are perceived very different in volume. So you can’t just set it to a certain number and be done.
The H90 also depends on how it is used (pre, post, pre+post, as a drive+boost, as a mod and ambient fx, etc.). Sometimes you may actually want the dynamic in volume. A Lo-Fi program using sticky tape doesn’t translate well when it is as loud as a lead sound for example.
Once you share a preset, it simply becomes impossible, because you don’t know what instruments, levels and overall setup the next person will use it for. If everyone used the exact same guitar, a guitar amp wouldn’t need a gain control (not talking about tone of course, just level).
To sum it up: I don’t think there is a real solution to this problem and you simply have to go through every program in your setup dialing it in using your ears and check levels and maybe even waveforms. And the next person will have to do the same. Describing your setup can certainly help others. And a looper makes it easier as well as you mentioned.
One thing I always do is to check for clipping. I hit the strings hard and turn up the output gain of a program in the H90 until it starts clipping, then dial back (6-12dB typically). That way I get a pretty good idea about how loud the program is in that very setting and go from there.
Hope that helps 🙂
