Newbie dumb questions

I am thinking about getting a QIDI X-Pro but I have a few stupid questions. First, if I want to print with just one extruder/nozzle, what is the best way to handle the unused nozzle? Do you just leave it empty? Do you heat it or leave it cold? Second, will hatchbox filament fit on the spool holders? If not, what brand of filament do you recommend? Finally, is there much of a problem with the nozzles being unlevel with each other? If so, is this something that can be easily corrected? I read somewhere that Qidi is now sending the x-pro out with the extruders already installed which might make this less of a problem...I don't know.Thanks for any help you guys can give. I appreciate it and will no doubt have more dumb questions along the way.thanks,Jim

I have a BCN3D Sigma dual extruder and the unused extruder remains cold. It can be empty or contain filament, but you don't want stagnant filament in the nozzle at extrusion temperatures. It will degrade very rapidly.

Nozzle alignment with respect to the bed is critical. There should be a means to adjust and/or calibrate for mechanical differences during the manufacturer and assembly.

Thanks for the great information, FRED_DOT_U. I will probably start out with one color PLA and didn't know what to do about the extra extruder/nozzle. Now I do. Thanks.