I don't see a lot of guys giving him trouble in today's landscape; Golovkin and Canelo could potentially make good fights but IMO both are too small and stylistically they don't have what it takes to get past the physical advantages he has over pretty much every middleweight ever; everybody else at 160 (even Jacobs) gets spanked.
SMW isn't particularly stacked at the moment but I think the super 6 era would've given us some fun matchups. Him versus prime Ward and Dirrell would've been interesting as they're both fast guys with good ring IQ (ATG caliber in Ward's case), I imagine they'd have something for him and I could even see Ward taking a couple fights off of him in a 10 fight series.
LHW is in an interesting spot right now, lots of good talent at the top but they're all eastern bloc fighters and I think the soviet school is not equipped to deal with Jones's skillset. I can't imagine Bivol, Beterbiev or Gvozdyk giving him a ton of trouble. 2013-2016 Kovalev is a much taller order considering his punch, his length (he's got shorter reach overall but seemingly longer arms than the others) and his movement (fencer like, similar to Jones), but I think his gas tank and inability to fight on the inside will be his undoing. Of the four though he has the by far the best chance of chinning Roy when he's pulling straight back, his power jab/left cross is also pretty sneaky and I think it could catch Jones off guard since he works it well into combinations where he's pursuing guys.