It's a bad idea to mix OS and personal data on the same drive.
The second SSD partition is used to speed up your work, backup should be done to the HDD.
Believe me, it's still a good idea in 2021, that's why there are graphical tools for partitioning.
If you work with different OS installations with different file systems, you have to partition your HDD/SSD to several drives. Perosnally I always have a partition formatted as FAT32 to make sure that the data on it can be accessed by any OS, even the deprecated ones.
Partitions are still the same physical drive.
The separation is much better done with individual physical drives.
I do that, see my parts list below. Each physical drive has its own use. CAD/Video/games/etc...
PArtitions on an SSD don't speed up anything.
Backups and how to do it is a whole different thing.
Not just an HDD in the same system.
What is your backup situation at home? And if you don't do that, why not? Every single day, I read multiple threads here of "How do I get my stuff back?" or "That drive had 5 years of photos of my kids!!" Be it a dead drive, dropped phone, virus, accidental deletion, formatting the wrong...
forums.tomshardware.com
Many people do partition a drive.
A lot of times, it ends up with one or the other 'partition' being too small. Wasted space.
Personally, I much prefer individual physical drives, rather than partitions on a single drive.
To each his own.