I just setup virtual Sierra and Mountain Lion machines under Catalina on a new Mac mini running Parallels. It works perfectly for me, and lets me use my old copies of VectorWorks 2008, Strata 3d cx and FileMaker Pro 11 which would cost more than $3000 to replace. It was not difficult to do, although I had to figure a lot of it out for myself.
I also have an old copy of Photoshop CS3 that I ran on my 2013 MacBook Air under Sierra but it was never as stable as it was on older versions of MacOS (such as Mountain Lion). Was going to run this on Parallels, but after some consideration I decided it just wasn't worth the effort, so I subscribed to the Adobe Photography plan. Like most people, I dislike software subscriptions, but for $100/year this seemed worthwhile and I'm much happier with the newer software. Anyway, I did not test CS3 on my virtual machine, but since my other high-end CAD/3d software runs I suspect it will work. If you're going to do this, I'd suggest using an older version of MacOS for the virtual machine, such as Mountain Lion, for better compatibility. The only caveat is that I don't know what graphics card/chip your new MBP has or whether that will be a problem (I suspect it will be fine though). My new Mini has integrated Intel UHD 630 graphics.
All of the articles I found on setting up virtual machines were based on using an original MacOS installer. But I found they could also easily be created from a clone of an old computer. Connect the disk with the clone and create a new virtual machine using the disk image/usb option in Parallels. That is really all you need to do to get up and running, but its a bit confusing. Actually, the vitual machine you create will not have an operating system and will just boot from the clone disk, so it only works when that disk is connected to your computer. But notice that it creates an empty system disk in the virtual machine. You can use Carbon Copy (time machine should also work) to restore the clone disk to the virtual machine and then it will work without the external drive connected.
Anyway, I'm very happy with how this works and it's saved me quite a bit of money on software I thought I'd need to update. Am also running Windows 10 under Parallels, which is noticeably faster than my old PC and works perfectly with my old software.