Elgato delivers support and a product you know will reliably work. The link you sent seems reasonable but has a ton of complaints about corruption, hard to use and not working on consoles.
As long as it's not the 1€ boards that just send you a pen. They will work but are usually rebranded boards with NO support. It's a risky move and I would recommend against it. If you're on a tight budget go for second hand.
It is with custom BIOS from before intel locked them. However, you risk bricking a board with a weird bios like I did 2 weeks ago... It works but is risky.
I have 300 up and down, I have not streamed in a while but I recall using medium settings and a bitrate that was not high. You will have to experiment a bit see what works best.