So for 4S or more, you want something like a 1600-2500KV motor. I've heard the 42mm motors need some clearancing done to get them to fit, but it can be done. You'll want something like the
Hobbywing 4268. The different versions support 6S except for the 2600kv which only support 4s. Or the
Tekin T8. But you'll notice they have lower voltage limits.
The Hobbywing combo is about $35 cheaper than the Tekin. Regardless of which one you go with, make sure you get the programmer (LCD box for the Hobbywing or Hotwire for Tekin), you'll probably want to make some adjustments to the ESC. And this is where the Hobbywing has an advantage because the Hobbywing LCD box can program in the field, where Hotwire requires a laptop unless you buy the pretty expensive bluetooth version.