Ronnie would probably be a great powerlifter. He hits great numbers in training now, and if he focused on PLing he would probably do better.
But, he would not be anywhere near as dominant in the world of powerlifting as he is in bodybuilding. Far from it.
He's pretty much the best bodybuilder of this era. As he stands right now, he would not really make a dent at the elite level.
Of course, this depends on what federation he's in. Since I don't think anyone is going to argue that Ronnie is "clean", lets hope its not USAPL, and just assume when we talk about international, elite level lifting, we mean WPO.
To hang in the WPO, no one is even going to look at him unless he's squatting 1000 (assuming the rest of his total is high enough so that he can qualify). Really, at his weight, he'd really need to be around 1100, and considering that there is an Israeli around his weight who is pushing 1200, Ronnie would need to be around there to be the best. Right now he squats mid 800 above parallel. Even assuming that he could get his squat passed at that depth, that puts him about 400 pounds beneath where he needs to be. That is quite a large margin.
For bench, repping 500 is a great start. Assuming he has time to learn a shirt and get proper carryover, he could be competitive, especially in full power meets where. However, there are some freaks out there who are benching around 800 in a full meet. If Ronnie truly wants to be the undisputed best, he would need to be around there too. That means, depending on where his 1RM is, he would need about 300 pounds out of his shirt. Thats definitely doable, since people have done it before, but not easy. Also a good way to get injured, but thats neither here nor there.
Also, since there are also guys who can bench 600+ raw in a full power meet, Ronnie would probably need to be able to do that too in order to compete with the best.
When you look at "bench-only" competitions, the competition gets even stiffer. Ronnie would need to be able to hang around 800-900 depending on his weight class. If he does "bench-only" in the IPA, he'd need 1000+ to be able to hang with Gene. To have the best raw bench, he would need to compete with Mendy's 700+ bench.
Of the 3 PL lifts, Ronnie's deadlift is in the best shape right now, although he would need to do it without straps. Also, just because he can double 800, doesn't mean he can do much more than that. The first rep of the deadlift is the toughest, so who knows. If he wants to be the undisputed best, he would have to hang with Bolton and Benedikt. Considering I don't know if Ronnie can deadlift 800 without straps, 970+ is a tall order.