FP4+ is the closest to Plus-X of any current film I know.
What I liked so well about Plus-X was how well it responded in Diafine. I sometimes preferred Plus-X at 400 in Diafine to Tri-X at box speed in normal developers. So this effectively gave me a medium and high speed film in one. I could carry Plus-X and rate it at 125 or 400 with abandon depending on the light I encountered, just mark it for development accordingly.
FP4+ is a great film, and I actually slightly prefer it to Plus-X at 125, but it doesn't get more than maybe 200 effective speed in Diafine so I don't bother, I just go to a 400 speed film at need.
I doubt I'd have shot a lot of Plus-X in sheets anyway where I'm shooting off a tripod and have more control. If I wanted/needed a medium speed film in 4x5 (the only sheet film I shoot) I'd choose FP4+ or maybe Acros. Plus-X could develop a rather pronounced shoulder. FP4 doesn't, and Acros is rather the reverse having upswept highlights.
I DO have some frozen, unopened boxes of APX 100 in 4x5, frozen since bought new in the 90s except for the few hour car trip to GA when I moved. I've been meaning to try it. No, I don't really want to sell it.