Apologies for not replying guys, I stopped getting notification emails.
I think i've got it fixed, for now at least - and I'll follow both your advice (s?) as well - thanks for the heads up Vol, i'm used to OBS notifying me. Then again, I haven't used it for a while.
I capped my FPS at 65, rather than the 69-70 I see it run at in game, plus dropped AA and shadows down a touch. Might not have needed those, but I will know after some further experimentation. So far, i'm down to 10 on CQP at 1080p60 recorded at 65 FPS with seemingly decent frames, lag, and quality.
Thank you all for your help, I'll report back again soon with more details as that's what I'd want to see in a thread.
Any further advice is and would be, as always, greatly appreciated. Thanks again.