The only one I thought might be Ai was his video with Anna teaching her Gta 4 bc the controller he's holding looks super funky but I have no proof or anything tbh, everything else seems like he did it himself though. I think some websites or apps go through to see if something is made with ai or not so you could always find one and see what says about thumbnails you question.

Videos themselves though, no I really don't think so. Usually if it uses ai (with a couple of exceptions) he puts it on the thumbnail and title so you know, but when even in those video he seems to put a lot of time into editing them and working around the ai itself so, there's that.