Actually this are same dilemma in the beginning for e power conversion. Most of them are on glow basis particularly 2 stroke. Say a 40 size 2c spin a 11x6 12k rpm.

It will fly extremely and a lot more scale with a 14x8 prop at much lower rpm.

For example my Kyosho Tiger moth. It call for a 46 size 2 stroke or 50 size 4c. Its prolly can swing no bigger than 12 in prop and need to rev fairly high to get a good thrust for the draggy plane.

I fly it on e power from day 1. My phasor 45/3 on 12 cell swing a 13x6.5 about 7000 rpm. Though at max rpm speed, the glow give more static thrust but its not useable because the plane will never reach that speed of 60mph, so its a wasted rpm where the epower max out no more than 45mph.

Same thing I guess for glow to gasser. I like to think the gasser as a big cheap 4 stroke. The glow fuel are just too expensive when you go above 90 size and when plane get to above 80in span.