It depends on how you define competent. You wrote a really good description of the dynamic between the two of you:
At the start of the day, I adjusted to his high 3b % by 4betting wider for value and more often as a bluff. He was himself 4betting so much that I started 3b/5b small pairs, but he adjusted by 4b/calling AJ, 77 etc so at this point I've readjusted by 4b/calling wide and never 5b bluffing. I think he'd cottoned on to the fact that I wasn't 4bet folding anymore so perhaps this explains why he peeled in this hand.
I think this suggests that villain
is somewhat competent. He is making adjustments to your play, and then adjusting further to your adjustments. This is extremely rare in poor players, and is usually a sign that an opponent is actually
thinking about his lines. Now you may believe that he is not always reaching the right conclusions with his thoughts, that he is overly spewy etc. And you may well be right. But we are none of us superstars. Perhaps he sees you in the same sort of way; as an opponent who is getting out of line, 3betting/4betting too frequently. He might feel that some of the hands in which he jammed light and you called and won were actually coolers given the dynamic between the two of you. And he might even be right in this.
When you get involved in highly aggressive preflop battles it is really difficult to work out the difference between correctly applied aggression and spew. And often there is actually not a great deal of difference. For example, the maths of 5bet jamming a rag Ace 100bbs deep is surprisingly forgiving in aggressive dynamics. You don't need a huge amount of fold equity given that you have ~30% pot equity when called (do the maths if you haven't already, it is super simple). You probably know all this of course. I am mentioning it just to make the point that
whilst you may very well be right about this opponent (and I am not arguing with your judgement), there is always a reasonable chance that you have under-estimated his level of skill and over-estimated his level of spewiness.
Obviously no-one can judge better than you where the truth lies since you are the one present in the moment and thus are able to feel the minutiae of gameflow. But just remember that it is always easy to be fooled in these sort of spots, so you really do need to play devil's advocate with yourself and constantly run sanity checks. Perhaps you have just been 'lucky' to have more than your fair share of decent hands when he has chosen to 5bet jam on you? And so his jams seem spewy because they don't get through as often as they 'should'. I am not saying this is the case obviously... well, you know what I am saying I hope.
It is hard to properly appreciate gameflow/dynamics unless present in the moment. However, when present in the moment it is often equally difficult to take a truly objective and non-results orientated view of a situation.