The just released 16" macbook pro has DDR4. They clearly aren't married to LPDDR.
The rated battery life of the Macbook Pro didn't change between 2017 and 2018.
I find myself scrambling for a power supply way more often than I ever did with my 2017 15" MacBook Pro.
Even with the older battery in the 2017, with more cycles, I get a longer battery life out of it than the 2019.