The factory triggers can be improved slightly, fine tuning, but replacement is really the “big knob” to turn if you want to improve the No.1 trigger.
I’m not sure anyone is still making set triggers for the No.1’s. I know Canjar quit around 10yrs ago, and I recall hearing around 5yrs ago that Kepplinger had quit. I’m not even sure Moyer is still making theirs - which wasn’t a set trigger, but rather a remake of the original No.1 triggers with adjustable sear engagement.
Jard and Brown/Eabco still offer No.1 triggers. These both are replacement triggers, similar to the Moyer which offer all 3 adjustment screws, but also with slightly varying geometries among the different pull weight models to improve leverage. Of course, the downside of the 3 screw model is the apparent ability, but realistic INability to control the sear engagement as a tuning point for a field rifle. For bench only, sure, cut your engagement down to 8thou and have a trigger which feels like a glass rod cracking instead of breaking... but risk slipping your sear if bumped in field use. But better is better, so personally, I’d probably buy the lightest weight offered in the Brown trigger from Eabco over the Jard, set it up how I wanted it for my use, and live happy.