The procedure for the STM32H750VB is the same as for STM32H750B. H7 graphics will not be available through CubeMX for a while, i think, so you cannot go that route. Are you looking at a custom board here?
That depends on what kind of application you're trying to build (complexity of graphs, animations, ..., your project budget, etc. E.g. if you're building a simple thermostat application you probably don't need an H750.
