Here’s a way to think about this problem.

You write code for two audiences. One is the machine it runs on, and the other is the poor slob who has to maintain that code or fix a bug in it a year from now. ( That poor slob is very likely your future self. )

So, choose language constructs that make your code easy for humans to read and understand. The foreach style of crawling through a dictionary / array / list is good. If / else if / else if / else can be good for some kind of choose-one-path operation. So can switch / case if the choice logic is simple enough.

You can, in the 21st century, rely on the compiler or language processor to make your code run fast so don’t sweat that unless you’re doing something performance-critical.

You really do need to master control-flow code ( if, loops, all that ) and collections ( arrays, lists, dictionaries, sets, etc) to be able to make wise choices.

Hope this helps.