Perhaps you meant -10? If you’re talking about the signal in front of the amp, yes, -10 will be the better option. If you’re also incorporating the effects loop of your amp in the rig, you may want to experiment running that loop at +4, as most amp efx loops run at line level, but it’s okay to try both and see what preserves your tone as you change the level of the Guitar preamp.
Yeah, it makes sense. That’s why I’d set the level coming out of FX Chain 1 to -10dBv if you’ll be directing that signal to other pedals. You’ll also have to experiment with the input setting on your drive pedal as well. But don’t forget the H9000 FX Chain’s output and algorithm levels can be adjusted, so I’m certain you’ll be able to find a good balance.