I am in the same boat. Got a Gen 4 19 recently and don't like the trigger nearly as much as my Gen 3 21. There are TONS of posts here with different recommendations on what the cause is, what to do, etc.
I called Glockstore and ordered a Gen 3 trigger/bar, a 4.5# connector, and got talked into a competition spring kit.
Hopefully one or all of these will smooth out the pull a bit. If not, I will at least gain some experience. This is my first attempts at do it yourself gunsmith work except for an extended slide release added to my 21.