Differences in designing a serverless function vs. regular server

Question

I am wondering what approach in designing serverless functions to take, while taking designing a regular server as a point of reference.

With a traditional server, one would focus on defining collections and then CRUD operations one can run on each of them (HTTP verbs such as GET or POST). For example, you would have a collection of users, and you can get all records via app.get('/users', ...), get specific one via app.get('/users/{id}', ...) or create one via app.post('/users', ...).

How differently would you approach designing a serverless function? Specifically:

1. Is there a sense in differentiating between HTTP operations or would you just go with POST? I find it useful to have them defined on the client side, to decide if I want to retry in case of an error (if the operation is idempotent, it will be safe to retry etc.), but it does not seem to matter in the back-end.
2. Naming. I assume you would use something like getAllUsers() when with a regular server you would define collection of users and then just use GET to specify what you want to do with it.
3. Size of functions: if you need to do a number of things in the back-end in one step. Would you define a number of small functions, such as lookupUser(), endTrialForUser() (fired if user we got from lookupUser() has been on trial longer than 7 days) etc. and then run them one after another from the client (deciding if trial should be ended on the client - seems quite unsafe), or would you just create a getUser() and then handle all the logic there?
4. Routing. In serverless functions, we can't really do anything like .../users/${id}/accountData. How would you go around fetching nested data? Would you just return a complete JSON every time?

I have been looking for some comprehensive articles on the matter but no luck. Any suggestions?