I would not upgrade the memory since it is unlikely to be an issue with performance. The original hard drive is the most likely item to be causing performance issues especially for a drive between 7 - 10 years old since the hard drive is most likely worn out or even failing. The greatest performance improvement will come from the SSD upgrade. Plus once you retire the laptop, you can remove the SSD and install it into a USB enclosure to use it as external storage for another computer.
The other most common reason for performance issues is third party software interfering with the normal operation of macOS. The usual culprits are anti-virus apps, cleaning/optimizer apps, and third party security software....none of which are needed on a Mac.
Once you install the SSD upgrade, use the laptop normally, then check the memory usage in Activity Monitor especially when you are doing a heavy workload in order to get a good judge of the memory usage. If the memory graph is yellow or red, then it indicates you may not have enough memory for the workload. If the graph is green, then check the "Swap" and "Compressed" values....if they are showing GBs of data, then it also indicates you may need more memory especially if the computer is having a performance issue.
Just remember such an old laptop will still have performance issues even with a SSD and memory upgrade so keep that in perspective.
If you decide to try an SSD upgrade, then the best SSD for price & performance is the Crucial MX500 series (avoid the BX500 series since it is a terrible model). However, many times you may also need to replace the internal hard drive SATA cable since that cable has an extremely high rate of failure on the 13" non-Retina model especially when using an SSD.
If you plan to use Zoom or other similar type of video chat app, you won't be able to blur or customize the background when using a 2012 laptop. You also want to check out the system requirements for all third party apps you wish to use to make sure you can run the very latest version of those apps under macOS 10.15 Catalina (especially for any apps which are used to access online servers & resources).
While I do like the 2012 non-Retina model, it is starting to get past its prime depending on how the laptop will be used. It will be fine for some things, but for other workloads it may no longer be up to the task.
As for security, the only thing you can really do is keep your third party software completely up to date. And practice safe computing habits as outlined in this excellent article written by a respected forum contributor (check out all other links within that article as well):
Effective defenses against malware and other threats - Apple Community