ESC Rating

4 in 1 ESC’s are rated by amperage, (ie, 40A, 60A, etc.).

Is this an overall rating or a per channel rating?

Generally, these are given per motor. However, make sure to have some headroom as they might be optimistic numbers (depending on the vendor) and check for continuous vs. peak.

It’s per channel maximum continuous current. Most venders will also label a burst current somewhere in documentation. Brands like holybro and flycolor are pretty reputable, though it might be better to use single ESC unless form factor becomes an issue or if you are really trying to cut weight. If one esc breaks on the 4in1, you pretty much have to replace the board. Which accounts to 4 times the cost of replacing single esc.