>>50554194yes and no. first of all, dynamaxing and megas are pretty similar but concept-wise dynamax plays a lot with the pokemon's design (making alcreamie a cake with lots of layers, garbodor a huge pile of trash, kingler turning into the biggest species of crab, etc.). so yes, most dynamax could've been megas.
ponyta turning into an eeveelutionesque thing is weird and doesn't make sense to be honest