Where does default compute and storage occur - on the cloud or local? How do I find out costs for AWS and adjust size of compute?
Well this depends on what Galaxy you are using. if usegalaxy.org then it is a combination of machines at TACC (https://www.tacc.utexas.edu/), JetStream (https://jetstream-cloud.org/) and Pittsburgh Supercomputing Center
(https://www.psc.edu/). but every Galaxy will have different resources.
This is a hard question and it mostly depends on how you use it (e.g. what tools on what data and how many jobs etc.)