Hi @leonardchiu
I haven’t seen this video you are talking about, so will definitely watch that. 
But I do have some answers for you, not saying everything I say is 100% correct but want to nudge you in the right direction.
1 scaling setup is meant for multiple servers, to spread the load of n8n workflows. Normally with small instances it is not necessary. I only use it when I know the instance is going to scale later on (or when it already needs it), to make it easier in the long run.
If 25 workflows is not something you are going to hit any time soon, you might be happier going with a normal non queue mode server. This of course depends on the number of executions and data load.
My setup is normally on EC2 (when using AWS) using a docker instance on there.
I like to develop en use custom nodes, so not sure if you can actually use a container server. As far as I have seen, you could not SSH into it or add persistent storage with a container service on AWS, so that makes custom nodes a bit annoying. Unless you create a custom image.
For a standard instance, I just put everything on 1 docker instance, often giving it a bit more resources to make sure we have some headroom.
For queue instances. I prefer to have a Helper server housing all the extra struf like Redis, postgres and all other things you might want to use like RabbitMQ. Of course also an option for using AWS database services etc.
Next to that Helper server we then have a server per main, worker etc.
Make sure to have 2 vCPU minimum per server, as we found an issue where the less than two can cause some issues when running with larger datasets. (Workflow on worker taking a lot more memory than on main)
2 Of course there cannot be documentation for every option out there, so that is probably the reason it isn’t there.
3 If you need more executions and/or workflows you can ask the n8n team for the pricing I think. So that should not stop you from going with the cloud offering.
If you require any mentoring or support with the deployment and/or the development of workflows, you can of course hire an expert. It can save you a lot of time. 
(you can of course PM me if you want to talk about this last part)