If you are in North America, all three model years for the HEV had the same 12V battery. The 2017 world model had a lead acid 12V battery. Not sure if there was a 2016 Niro overseas, but if there was, it would also have a lead acid battery. I suspect there was one overseas as my dealer had a showroom model with one before the 2017s came out that had to be returned to Kia without selling it. The 2016 Ioniqs all had lead acid 12V batteries.
The only significant model change I know of is that the 2017 did not have LKAS as an option in the US (other countries did have it). That is one reason I waited until the 2018 model year to buy. Not a huge deal, and honestly it is a bit annoying to feel steering wheel adjustments. But if it saves your life just once...
Trims do change (and their options), and the later built models will have corrected earlier issues. The door handle was over torquing a nut, easy adjustment at the factory. Fixing a broken door handle was also easy, except for a poor supply chain.
2018 Kia LX HEV Metal Stream with Advanced Tech