TechT bolt first. Best upgrade for it in my opinion. Make the shot sooo much smoother and quiet. OLED is not absolutely needed, but a new board is a plus. The OLED is nice so you can see which mode it is in at a glance. If you can afford it, get it
The CP trigger is real nice. The shape makes for a much better feeling pull. Which the new board will help with as well since it will have a microswitch pull as opposed to a sensor. The microswitch feels sooo much mo better.