I have all 3 (and big hands).
19 - if I only had one handgun, it would be a 19. As a concealed carry gun, I think the micro 9s are better options. My carry is a p365. I shoot a 19 fine, but prefer a factory plus 2 mag for a bit of extra length on the grip. If you are running an x3000 you give up a compactness advantage.
45 - I shoot it as well as my 17 and better than my 19. Most people say the extra grip helps shootability and mine is one of my more inherently accurate glocks, meaning it shot very tight groups straight out of the box. Slightly shorter sight radius, but that won’t matter if you shoot an optic. Conceals better but you give that up with a x300.
20 - 10mm is a different animal than 9mm. Power, recoil, ammo costs, shootability. There are better opinions than mine about 10mm for animal protection. I would not feel undergunned with a 9mm loaded with hard cast in the back country, with the exception of brown bears. Opinions vary on 10mm for brown bears and I would agree that bigger would be better. However, I have enough time behind glocks to feel more confident in my ability to mag dump a g20 into a bear more than 5-6 44 mags. YMMV. FWIW, I carry my g20 when I am in bear country.
PS buy the g45. The answer is never NOT to buy the new gun.