I don’t have experience with genetic dwarfs. However, any weak growing apple scion will produce a much smaller tree if grown on it’s own roots. Whether it’s small enough for your needs I am not sure. Honeycrisp is a good example of a low vigor scion. But in most cases people use dwarfing rootstocks to reduce tree size.
You could look at this list for low vigor scions.
Also look at this calculator it has some low vigor scions listed.