It’s always best to follow the standard install document (discourse/docs/INSTALL-cloud.md at main · discourse/discourse · GitHub). Third party installers are likely to be out of date, and not supported here.
They are innumerable.
My recommendations are to start with the simplest configuration possible, a single server using the standard Docker install. For a frame of reference here’s a list of how I charge for installations.
For most people, I recommend Digital Ocean because it’s reliable and simple to configure.
If you have hundreds of thousands of page views daily, or a community that’s geographically diverse, a more complicated setup may be warranted.
You can use RDS and Eleasticache, but you’re mostly on your own to figure that out. There is some discussion about scaling over here. Mostly, unless you have wildly varying needs (e.g., hundreds of thousands of people pounding your site for a couple of days and then little traffic the rest of the time), auto-scaling more trouble than it is worth.