This is really awesome and I might try it (definitely bookmarked)

This might seem (offtopic?) but you mention railway and how for a 20mb app the costs become almost negligible and I got curious because I usually refer hetzner to be one of the cheapest but still good/well worthy solution

I find the pricing model of railway the most interesting. I am curious if you know of any other alternatives to railway which follow a similar pricing model as well as I'd like to compare if there are more of such cloud providers which provide this (preferably from a service which is more closer to bare metal than y'know cloud providers perhaps if that makes sense)

Agreed. So much easier with self hosted runner. Just get out of your own way and do it. Use cases like caching etc also much more efficient on self hosted runner.