Ahh I get it. I thought the quick menu was the core options. I'm still finding my way around - there's a ton to retroarch!
Regarding runahead, I gave https://docs.libretro.com/guides/runahead/ a good read. I didn't try calculating the amount of runahead needed to offset the latency, but I just tried it set to 1 and the game and audio stutters. My Pi is currently setup stock speed if that matters.
Also, if I enable a second instance in there, I get Failed to create second instance.
Found the retroarch config thanks for the fps. So many places to set stuff.
Cheers!