Snidal doesn't list a torque for either.
I think most folks just go by feel. The main thing is not to be a gorilla.
On the screws/bolts, I just go a little past stop. Tight, but I could go tighter. There's no real oil pressure there, and you're screwing into aluminium threads. Just enough so things don't leak.
The spark plug I do a little tighter. The point is to compress the ring to make a good seal. The spark plug isn't in danger of shooting out, so don't tighten it up until your really leaning into it. Until it stops and a half turn is good. Yopu shjould be able to feel the compression ring mashing down.