external drive for different platforms

Hello hive mind!

I use a 27" imac with 10.13.6. It works ok but is slowing. I haven't updated to any higher OS because I have a version of the Adobe CS 5.5 that I own that I use every day that will not work on any higher OS>

I spend 6 months out of the country and I take a laptop with me that runs something like 10.15. In order to be able to use the CS I have an external HD that I scavenged out of a dead laptop that is bootable and runs the 10.13.16. It connects to my laptop via the USB port. I set the boot drive as the external HD and unplug it from the laptop. When I boot normally the laptop uses the internal HD and if I need the CS I turn it off and reboot with the external. But it's S L O W for a refresh rate and if I use an external monitor it flickers and drops out and goes to black screen sometimes. NOt always.

I am considering this solution for both machines:

"the cost-effective solution to your speed problem is an external USB3 drive enclosure with an SATA 6GB solid-state drive inside, then set as the boot volume. That will increase your data transfer from the current 70 MB/sec to around 400MB/sec with a remarkable improvement in how fast your computer responds."

Will this work with both my 2013 imac and my 2011 laptop? I am concerned that I don't have a port on either machine that will support the USB3 connection to the external drive.

Thanks for any advice. If someone had any ideas of how to make the CS5.5 work on the higher OS level machines I'm up for that to.... but I think that boat might have sailed. Years ago. sigh