You'll be wanting to upgrade your 16" MBP for a future model with a better dGPU sooner than you might think given how painfully weak the 5300M & 5500M are. Unless you are immediately going to need 32-64 GB RAM? Stick with 16 GB. The release of the 16" MBP was a great return to form for Apple's Macbook Pro lineup, but given AMD's huge shortcomings with their GPUs? Don't expect the dGPU inside the 2019 16" MBP to be relevant next year if we're being honest with how much better of a dGPU will come in next year's Macbook Pro lineup, so maxing out a 2019 16" MBP might not be the best idea because the dGPU will age like milk left outside the fridge.
Huge shortcomings? These cards are actually competitive and represents the first time you can actually game on a Mac. It’s a modern 7nm AMD chip that competes with a 1060 desktop card.