Garage heat

Electric........there is no magic. "So many watts" (amps) = so much heat. There is no such thing as a magic more efficient electric heater. Heat is about 3400 BTU per kilowatt, PERIOD. A typical bathroom / portable heater is about 1000-1500 watts if that gives you some idea. A leaky uninsulated garage? Almost zero effect. A 1500W heater is going to draw about 13A at 120V so you've "used up" one 15A circuit right there

Consider LPG Maybe score a used heater/ furnace VENTED if possible. Portable / infra red / salamander stuff can be an explosion/ fire hazard when coupled with solvents, etc.

NAT gas, do you have it in house? How far is the garage? I have no workable shop, but I have a big shed I heat when I HAVE to, with an old nat gas furnace. I "cheat." I installed a nat. gas "barbecue" quick connect and valve outside the house, and then scored a big length of barbecue gas hose. I just hook it up when I need it

Oil.....Might look for an old but servicable oil furnace. "If you are handy" you can do some research and install it in one corner

Wood...already mentioned.

I have NO idea the codes you are fighting, I bet it is "plenty." If you are doing ANY painting/ solvent/ other flammable, ANY unvented combustion heater and some electric heaters will be an ignition hazard.