For that CPU either motherboard would work great. I'd prefer the B450m Pro4 in consideration of future CPU upgrades such as 3700X, up to even a 3900X which might be pushing it but would work if also not overclocking.
ADDED: When you say you're not overclocking RAM, that means you'll run it at an anemic 2133 DDR4 stock speed. Running it even at the CPU's rated RAM clock speed (I believe 2666 for 1600, or 2933 if it uses the Zen+ rating) is technically overclocking.