Good idea, however remember to calculate power requirements in the DC and get at least 100% more space than you currently need!

I've seen cases where you want to provision the new rack but unfortunately DC is full and you have to end up running infrastructure spanning across different buildings or even different DCs.

With Zen4 I would go with single CPU option, it's hard to saturate 256 threads.

Main cost in the cloud is always the database server, because it needs to be on 100% of the time, cannot be on spot instance, and needs lots of memory and CPU just in case of a spike of traffic.