Do you mind including your budget in the OP? That would help others do their own calculations on electricity savings vs cost of hardware over time.
I've been monitoring this page https://gist.github.com/ironicbadger/5da9b321acbe6b6b53070437023b844d from https://yewtu.be/watch?v=ceUIUyZwchY
It's showing some really interesting results for various processors and their efficiency while transcoding.
I have no idea. I think if you're a paying customer, they might be more inclined to allow installing plugins.