I owned and ran a burger food truck for 7 years, mild cheddar will melt.......somewhat, it's waxy and oily.
My default cheese was American, a high quality brand is a must.
Don't hold burgers in a chafing dish, I wouldn't buy one. I can get that at Micky D's
People WILL wait for a good product, my wait was 20-30 min when I was busy, people waited because they knew what they were getting.
Don't get crazy with flavored salts, no one will taste it on the burger. Save that...