First thing to consider is that the "off season" isn't a thing like it is in other sports. There's no powerlifting season. I understand the term to refer to training when you're beyond a certain point out from a meet, but there's no standardized definition or anything.
Second, "is it worth it to train in the off season?" As in, should you stop lifting weights if you do not have a meet scheduled? No, I don't think that's a good idea. As Mike Tuchscherer says, "progress is made in months and lost in weeks."
In general though, outside of meet peaking, I think more bodybuilding-type work, and a heavy emphasis on close variations (e.g., SSB Squat, Snatch-grip dead,) are good ideas. Everything depends on the overall training philosophy though. Too broad a question to answer more squarely than that.