> Thunderbolt 3 -> Thunderbolt 2
> Thunderbolt 2 -> FireWire 800
> FireWire 800 -> FireWire 400
> FireWire 400 -> Mini FireWire
Ummm... Lol yeah I suppose you could do that.
I just used my old 2010 MBP which has a firewire port :)
But indeed older Macs are pretty ideal for this as FireWire is an integrated part of the ecosystem.
What was actually quite difficult is obtaining old versions of iMovie and QuickTime. I still had the old OS images, but Apple makes it impossible to get old versions from the app store. If you look for iMovie it just shows the latest version which is no longer supported for my old macOS (the latest my MBP could run) so it's a dead end.
Eventually I found a link on Apple's site with a ZIP file of the iMovie files, and I needed to do something else to actually make it work (extracting and moving to /Applications wasn't enough). I don't remember exactly. It was a bit of a PITA but in the end I got it.