SSD Partition (New Mac User)

I never recommend partitioning any drive because people sooner or later realize one or more partitions are too small and fixing it requires starting over again.

With the APFS file system on macOS you can instead just create a new APFS volume which acts a lot like a partition, but doesn't require you to decide on any sizing. All APFS volumes within a single APFS Container share the same storage pool, however, the files stored on each APFS volume are separate. Plus the APFS volume can be mounted & unmounted individually or even have one APFS volume encrypted using Filevault while leaving the other APFS volumes without encryption.

Add, delete, or erase APFS volumes in Disk Utility on Mac - Apple Support

Just make sure to always have frequent and regular backups of your computer and all external media (including the cloud) which contains important & unique data. There are a lot more new ways to permanently lose access to the data stored on the internal SSD of the recent Macs due to all the hardware, software, and security changes. Apple includes Time Machine backup software with macOS, or you can utilize a third party option as well such as Carbon Copy Cloner (CCC) which is extremely popular among macOS users.

Yes, it's possible.

You can use Disk Utility to partition the drive, but you will have to do so from Recovery.

Hold down the power button when turning on the Mac until you see the boot options. Click on Options and then on continue to load recovery.

click here ➜ Partition a physical disk in Disk Utility on Mac - Apple Support

Also, in general on macOS needing to re-install the OS is fairly rare, but it's always good to have an external backup regardless.

Reinstalling macOS does not have to involve wiping the user data. Reinstalling the OS simply lays down a fresh copy in place of the old system on the current system drive. The way the Mac startup drive is configured these days is with the OS on its own write protected volume and the user data and other ancillary components on their own individual volumes, but all within the same 'container' and sharing the available storage space.

With Apple's APFS drive format, the drive is partitioned into a container within which five separate volumes reside. There is a volume for the OS, one for user files and data, and others for VM, Preboot and a Recovery partition.

The APFS format allows one to add and remove APFS volumes at any time without reformatting the drive device.

Apple provides guidance on using APFS volumes here: Add, delete, or erase APFS volumes in Disk Utility on Mac - Apple Support

Partitioning a drive device really is no longer necessary except when setting it up for Mac use the first time. It's much easier to add, delete and erase APFS volumes as needed than it is to repartition a drive.

<< if I ever need to reinstall macOS, my data won’t be deleted. >>

By design, Re-installing MacOS has NEVER touched user files in any way. You have always been free to re-install macOS (same or later version) without ANY impact on User files and Applications.

From MacOS 11 Big Sur onward, the system is on a separate, crypto-locked System Volume, which is not writeable using ordinary means. Any unauthorized changes to the crypto-locked volume are quickly detected and you are alerted.

So you could store just about every malware known to mankind on your Mac, and your Mac would not get infected spontaneously. Scanning for virus-like patterns might make you feel a little better now, but non-stop scanning is outdated nonsense, and a tremendous waste of resources.

Nothing can become Executable Unless/Until you supply your Admin password to "make it so".

Everything you need was already shipped in the box. Except one item -- an external drive on which to store backup copies of your files. The very good backup Utility, Time machine, is included free. It is integrated into MacOS and all you have to do to "make it go" is provide an external drive and tell it to go.