S19 and S19j Comparison

What are the key differences between the S19 and S19j beyond just power usage and speed? I’m curious if anyone has insight similar to what we saw with the S9 models: like the 14th being the top tier chips, the 13.5Th being from the initial run, and the 13th being the lower quality ones. I’ve been pretty happy that most of my S9s are from the 14th batch. A lot of them still work quite well at 7.9V, while the 13.5s and 13s usually don’t perform as efficiently for the same TH output. So, anyone got some knowledge or even some educated guesses on this?

Probably not completely relevant, but while perusing ebay for miners I came across a selection of listing for the asic chips themselves. The listings had different number chips for different iterations of the same miner. So its probably not as clear-cut as most think.

I wouldn't be the least bit surprised if the J models were just amped up standard models with fewer chips.  But that is just speculation.