Are there guides to this that take you through good configs for smaller environments like this? i.e. you have a postgres DB and two web servers. What's the simplest backup process and how do you replicate to another DB VM over on another VPS provider securely?

Stuff like this is relatively simple when you are trying to learn it, but keeping it operation is hard at a small level. Is the less to really use PaaS until it's viable for you to be running a small K8s cluster, or equivalent fleet? Seems really expensive compared to VPSes, but having better guides might help.