For production or a one-off? The reason stm lists a maximum is because that's a guaranteed maximum. You might find that the ability to over-over drive the chip is not consistent. Note that 480Mhz is already considered overdriving and is only available if you are using the LDO.
Not clear where the critical paths are, likely the prefetch out of the cache. Might also be some on the peripheral sides which also limit top speed.
The 400 MHz parts had a much higher ceiling, but ST hasn't really discussed the design issues with the H7 which seemed to take several years to get properly resolved.
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I am just getting started with a h745. They are truly amazing chips and really make me wonder what sort of magic is going on inside. I'm particularly impressed with the real-time capabilities of the d2 domain. The block interconnect, dmamux and dmas makes the chip somewhere inbetween a microcontroller and an fpga.