I used a torch for years. Frankly, I use my m18 fuel grinder with a cut off wheel more than anything. Unless I’m cutting a pattern or plate, the m18 gets me by (and is quick!)
I tried the diamond a while and went back to the diablo 5”, 1mm thick abrasive wheel. They cut like a hot knife and being relatively thin require less energy (that’s great for the battery.)
Another great thing to save are the cut off pieces shaped like triangles (of all sizes)
I have a 5 gallon bucket of these and are my go-to for gussets.