"I was under the impression that I was unable to install new Mac OS software because it would cause issues. Do you have any opinion on this?"
Have you TRIED updating it?
Do that, and get back to us.
You should be able to install any version of the OS onto the SSD, that the Mac will run.
I would suggest OS 10.12 (LOW Sierra) as a "good move upwards".
You can get it here:
https://support.apple.com/en-us/HT208202
IMPORTANT:
BEFORE you update, I STRONGLY SUGGEST that you use either CarbonCopyCloner or SuperDuper to create a bootable cloned backup on an external drive.
Either app is FREE to download and use for 30 days -- the backup costs you nothing (provided you have an external drive).
Having a bootable cloned backup will makes things relatively easy to "get back to where you once belonged" if the upgrade doesn't go as planned.
No cloned backup?
Then "getting back" will become MUCH more difficult.