Never had a problem yet except for UEFI boards which have no legacy CSM. Except some of the truly well-engineered UEFI firmwares do boot from a FAT32 external MBR volume. Otherwise no DOS for you.

Just use CSM and leave it in SATA mode and the A: drive, plus FAT volumes on HDD/SSD's are accessible and enumerated conventionally as C:, D:, E:, etc. according to legacy hierarchy on each boot. Remember to have all but one of your primary partitions hidden per HDD while in DOS. Carefully go wild with logical volumes often beyond 120GB offsets.

For best reliability I like to format FAT volumes using the MSDOS from Windows 98SE, only up to 32GB, especially to format USB sticks. Above 32GB I use NTFS and format using Windows 11. Alternatively the long-lost Iomega fat32 formatter would go way beyond 32GB using alternative cluster size far more reliably than Windows ME which was made for 64GB max. Always use the Scandisk fom W98SE, not WinME DOS for anything. Sometimes partiton in DOS FDISK too but more often using good old Linux Mint 9. Mint 10 is just as good for partitioning, but mkfs vfat declined in useful granularity at that point. Remember the live distro of Mint 9 doesn't support USB3, so use a USB2 socket for that. Etcher just doesn't cut it by comparison, use Rufus if you can't do it manually on your own. Most often zero whole drives before partitioning, and zero whole partitions before formatting. Much better off without pre-existing stray boot sectors, FATs or MFT's scattered around in the middle of your volume to take your data by surprise. Also many USB sticks formatted from the factory have a defective location for the backup volume boot sector if there even is a backup. Microsoft dropped the backup boot sector themself when formatting FAT32 with the release of XP, seems likely intended to compromise FAT32 reliability and make slower NTFS seem more acceptable when pushed into the mainstream back then.

Things like Windows XP or older won't install or run in SATA mode without a proper driver floppy for F6'ing, that's when it's easier just to use IDE mode sometimes. Also can be more challenging to add SATA drivers after installing though, and you usually end up pointing to the same files the floppy has on it.

Also the undocumented DOS command FDISK /MBR writes the high-reliability DOS MBR to sector 0 of your "master" HDD, of course without touching the partition table. This can only be accomplished from floppy.

Then DMDE disk editor has a DOS version made to run from floppy. Careful usage up to 120GB often but usually just access sector 0.

Things like Battle Chess or Tetris need no introduction, people can be highly amused booting & running it from a floppy whether or not a PC has any other drives or not. I'm partial to the DOS versions of the old 3M Bookshelf board game Acquire, all about investments, shareholders and mergers. Everyone prospers (at the end the bank might even run out of the originally provided paper currency, and you certainly will endure zero cash yourself before recovering during play) so it's more fun than the appropriately named Monopoly, plus it always goes to a direct ending usually in an hour or less. Most money-making person still wins.