I love my Glock 17 (9mm). At first, I was shooting tight groups but low left as you mentioned. Then I learned this is due to a tight grip. I loosened my grip a little and saw much improvement.Are the rounds consistently hitting, say low left, if you are right handed for example. It is easier to diagnose some shooting errors by where the rounds hit compared to where you are aiming.
The trigger is going to be wildly different that a nice tuned 1911 trigger and takes some adjustment as stated above.
I do love my Glocks!!