A parallel solution to what you use for your PC would work fine. Using the same drive will not work at all.
To use as a Time Machine backup drive, an external drive MUST be formatted as a MacOS extended Volume. Also, Time Machine adds incremental changes to the backup drive over time, so the size of the backup keeps growing until backups are automatically consolidated due to their age. so storing "other stuff" on the same drive is losing proposition.
A drive 2.5x to 3x the size of what needs to be saved will provide ideal, trouble-free operation. You can get by with a smaller 'found' drive for a while, but when you upgrade your Mac or your MacOS, it will need to store old plus new plus some slack.