Round trips between the form and the Anvil server are usually the bottleneck.
The best way to optimize performances is to collect all you need inside one dictionary, make one call to one server function, the server function will use the dictionary to do whatever it needs to do, then gather all the info it needs to gather, collect it inside a dictionary and return it to the client.
This way you have one round trip only. It might be slightly slower, but it will usually be much faster than splitting the work into several server side functions that require several round trips.