If you have a Mac Pro, you can add USB 3 via a card (see sig); PCIe 3 isn't an issue for video, you can't saturate a PCIe 2 bus in 2021: with storage, you are limited by the speed of the hard drive (I did a RAID0 boot drive to help with this - I could reach the SSDs max read/write); Thunderbolt is still (and always will be) a solution in search of a problem. NVMe is in the same boat. AFA needing HEVC encoding - that is a choice. If you need that - move to windows. BTW, in windows everything just works. No need to spend time trying to jury rig something for a decade old computer. Added bonus, Windows 10 is as bullet proof as Mac OS. (I never thought I would type that, but here we are.)
You appear to only do one thing at a time on your computer. That is a side effect of only having 8gb. When I first installed OS/2 in 1992, I left that world behind. I have my entire workflow open simultaneously (6 or 7 apps), Cntrl-tabing between them as needed. That isn't an option on 8Gb (or 32Gb) of ram. As a minimum, it will help with reducing the time for task completion. Which is important if you value your time.
Again, it isn't about what you need today, it is about what you may need tomorrow - having to think about this is one of the many downsides of having a sealed system with no ability to upgrade - the computer becomes an appliance, and is limited in what it can do.
I have been down this rabbit hole with my macbook pro - hence my suggestion to max out any system you get. Every time I increased memory, I got more performance.
AFA getting a new system, if your needs increase, how long will it take for the next generation of Apple Silicon hardware to show up? Apple doesn't do road maps, so you could be stuck with that computer for YEARS. How long between the 6,1 & the 7,1? Oh yeah, over 2,000 days. Obviously, that won't be an issue for Gen 1 (It will have it's own problems, if past performance of V.1 Apple Hardware is any guide), but how long until Timmy kicks out version 2?
I was able to nurse those Mac Pros for over a decade because I nearly maxed each of them out. By the end of 2019, it was more trouble than it was worth, and I replaced it with a real computer. Outperforms any Apple Silicon based computer, for the price of a bottom of the barrel MacBook Pro.
And I can upgrade both the CPU and GPU (ram is already maxed out) as needed, saving me a LOT of money.