@Jake Ladley I dont want to hijack the thread so short answers for your question: Windows build is only an option included lately, for me and some users as an alternative. The fork was started and optimized for Rpi and using multithreading to enable tone mapping processing. I'm using ezcap 269 but had some feedback that it work for many modern HDMI grabbers for example MacroSilicon MS2109 clones.
And back to the subject: dont give up on the grabber before you can exclude software or some settings. Even cheap MS2109 has a lag only about ~100ms.