What are you hoping to get out of the upgrade, and what hardware does your current system have now? Are you planning on upgrading any other components?
Considering how close the performance of a Ryzen 3600 is to a 3600X (typically within a few percent in CPU-limited scenarios), it's questionable whether it's worth paying an extra $40-$50 (20%-25% more) for that part.
Also, B450 motherboards should be able to handle these processors just fine with a BIOS update, and some, like MSI's B450 Tomahawk, can have their BIOS updated using a thumb drive without the need for a 1st or 2nd-gen Ryzen processor. Those boards don't support PCIe 4.0, but the benefits of that interface will likely be minimal for some years to come.
VRM temperatures probably don't matter much for the 6-core, 12-thread parts either. That's likely more a concern for the higher core-count offerings, like the 12-core, 24-thread 3900X, or the upcoming 16-core, 32-thread 3950X.
If you have a limited budget for the upgrade, a 3600 with a B450 motherboard would cost a lot less while offering a similar level of performance. And that money could be put toward other components, if needed.