Clarify which paths (from CDK/copilot/CFn) are necessary vs optional

[ohookins]

Maybe this will become more clear as the workshop progresses but I've found that it's not super clear which of the copilot/cdk/cloudformation paths are truly optional. I took a look at the resources configured by the CDK instructions vs the Cloudformation templates and found that they are different - so it seems that both are required. Similarly, I was not sure that the Fargate vs EC2 modes were alternative options so I tried to deploy both before realising that the stack name was the same - and ended up with a stack that couldn't be deleted due to some awkward dependency issues (which is never fun to resolve manually).

Perhaps this is just my misunderstanding, but I think having some additional clarification around this would be helpful.