Some confusion over the use of coordinating and subordinating conjunctions

Teachers, could you please help me with the following things?

1 = Is the coordinating conjunction "and" in the following sentence joins or connects the whole preceding clause "They went to the cafe" and the predicate "had some coffee" or does it join or connect just the two predicates, i.e., "went to the cafe" and "had some coffee"?

Here is the sentence:

-They went to the cafe and had some coffee.

2 = I've got to know that that a subordinating conjunction joins or connects a main/independent clause and a subordinate/dependent. I have some confusion over this, however. Take a look at what I've said bellow, please.

How do we know or determine which of the two clause that it joins is independent and which is dependent? For example, we have two clauses: She was unhappy. She was rich. Both of these clauses are independent. When we join them with the help of a subordinating conjunction, for example "although", the resulting sentences might be: Although she was rich, she was unhappy.

She was unhappy although she was rich.

Here, how do we determine which clause - She was unhappy? or She was rich? - is independent and which clause is dependent?