Cold gas thrusters are as reliable (because of simplicity - basically just container of pressurised gas and a valve [1]) and as precise in their thrust pulses execution as it can get. Better precision in thrust execution probably only ion engines have but just because of extremely low thrust levels in general (milli-newtons).
I saw a really good YT video a few months ago that explained this very well. Went over all the fuel types and tanks and propulsion designs.
Started with what you said - a simple gas pressurized and a single valve.
Slowly more and more was added until we get to current rocket designs with multiple stages or active pressurization / fuel transfer and all that entails.
1. https://en.m.wikipedia.org/wiki/Cold_gas_thruster