ADC has a few quirks, parallel conversions on more than one ADC is practically unusable. Converting channels on a single ADC works fine if the analog supply is free from noise.
SDMMC works fine, maybe not at the theoretically possible highest data rate, but mind the L1 cache and the bus matrix constraints.
I2C is difficult to get right on all STM32 series, not specific to this MCU. Following the reference manual very closely usually helps.
Lots of users are having problems because they forget about the L1 cache and its implications. These problems go away when the memory buffers used by DMA and other bus master peripherals (SDMMC, USB, Ethernet) are properly configured as non-cacheable. This is specific to the F7 and H7 series, i.e. ones with Cortex-M7 core.
In general, most of the problems seen on the net seem to be related to a certain software library. Apart from the high number of bugs, it is quite poorly documented. When something doesn't work with the library, poor users are trying all sorts of hacks to make it work, sometimes it's impossible to tell whether there is a library bug, improper usage (lacking documentation, there is little agreement on what exactly proper usage is), or the feature was never meant to be supported by the library at all. Again, this is not specific to the H7 series, and the problems are not present at all when one sticks to the register interface as documented in the reference manual.
I know next to nothing of PCB design, but maybe a hint, arrange an "analog only corner" around pins 15-35 (up to 43 if using the comparators) to reduce noise on ADC.
