To your first question, Yes you can. The volume on the Helix you can have it as a Master Vol. Go to Global Setting and on page 2, there will be a setting for the Volume Knob. Change that to 1/4". (Make sure your volume is all the way down on the guitar and amp). And, For you 2nd question, I don't think you can, just yet. You can link two pedals together, or have one turn on while the other is off. vise, versa.