12v wiring

[CraigCam]

I'm replacing all the wiring in my 1970 overlander. I'll have a professional do all the connections to the inverter/ batteries etc. I'm trying to figure out how many Lights or 12v appliances I can have on one circuit? I have the same question for the 120v circuits?

[GMFL]

All will be based on max amp draw. You will need to figure the max amp draw of each item and the plan to only use 80% of the fused circuit. (20amp fuse, wire for max 16 amps)