Since you bought a tactical model 1911, I wouldn't replace anything right away. And the words "drop in" and upgrade usually don't fit well with a 1911. Any real upgrade will end up being fitted to the gun. RIA triggers have a decent reputation for a good pull out of the box, but to get a better one is going to require a smith who knows 1911s, and good trigger, hammer, sear, disconnector at minimum to all be fitted together. Sometimes a new safety is required as well.
About the only other upgrade I can think of is good quality night sights.
My "tactical" 1911 is very simple. Good trigger, good safety, good sights, good grips, no rail, and been fed lots of ammo without choking.