Grammar question regarding an additional comma

Hello, I have a grammar question regarding an additional comma.

1. We now have the value AB, where A is abc and B is edf.

2. We now have the value AB, where A is abc, and B is edf.

I am wondering if the additional comma after "abc" in 2 is OK.

Similarly,

1. If A is abc and B is edf, then we have the combined value C.

2. If A is abc, and B is edf, then we have the combined value C.

I am wondering if the additional comma after "abc" in 2 is OK.

I am also wondering which one (among 1 and 2) is more commonly used.

Thank you.