Yes, 4x2A charging posed no issues for me. Possibly even 4x2.5A may have been OK - I have not tested that yet.
In all honesty though, I don’t see myself needing to use 4x3A much if at all. I don’t own any cells larger than 18650. A typical high drain 18650 has about 3000 mAh capacity. It’s not going to be that much quicker to charge it using 3A vs 2A or 2.5A. Now, if you own large 26650 cells with 5000+ mAh capacity, that difference in charging speed will become more noticeable.
Correct.