[aappleby]

A GPU with a dedicated encoder for x264 or preferably x265/AV1. You can do without it, but you'll spend a core or two on software encoding and the overhead will add a few tens of ms of lag.

With full hardware capture and encode (default on windows, can require tweaking on Linux ) it's virtually free resource-wise.

[ThatPlayer]

You're off by one letter: the codec is h264/h265. x264 and x265 are the CPU encoding softwares for the codec.