Depends on the class. Most of the 1/10 that I race are between 20-30mph.
I’ve run some classes that hit 60-65mph. My club doesn’t have any classes hitting those speeds but a local outdoor club does.
My 1/28 can hit 20mph depending amount of upgrades. The one I race hits maybe 15mph, but to scale that’s faster than the 1/10 I race. Some of the very highly modified 1/28 cars can supposedly hit 60+mph, but no one locally races those particular cars and I’ve never seen it.