I got As in statistics and math. I got As in statistics, stata and math. I got As in two subjects. I got As in three subjects. This implies that you studied more subjects, but only got As in 2 or 3. We don't know what other grades you got. I got As in both subjects. I got As in all three subjects. This implies that you ONLY studied 2 or 3 subjects, and you got As in everything! (p.s. I am not sure what "stata" is - not something I know in English...)

For the first part of your question, 'I got two A's' is what most people would say if it was obvious you were talking about exam results

As it would normally be obvious that you were talking about exams 'I got two A's' would be fine

I'm not sure about "benchmarking" as being the best way to describe something. But for the verb, you could say This job requires benchmarking. This job includes benchmarking. This job entails benchmarking. which have slightly senses.