As a general rule, as long as the oil pressure stays above 15 psi, you should be OK. As an engine wears out, the oil pressure tends to drop because of increased clearance in the crankshaft bearings. Most oil pressure idiot lights don’t come on until down around 10 psi or lower.
As for the idle speed. On the side of your throttle body is a device called an Idle Air Control, aka IAC. It is a small valve with a stepper motor that opens and closes the valve. With your foot off the gas, the butterfly (throttle plate) in the throttle body should be completely closed so that the IAC controls the amount of air that gets into the intake manifold.
The IAC stepper motor is controlled by PCM (powertrain control module, aka the computer). But it only controls the IAC when your foot is off the gas. It gets the information that your foot is off the gas from the throttle position sensor (TPS) in older cars, usually pre 2006, or from the accelerator position sensor on the gas pedal in newer vehicles with “fly by wire” throttles.
The throttle body has a throttle plate stop screw that resembles the old idle adjustment screw on carburetors. It is sole to prevent the butterfly from closing too hard and damaging the soft aluminum throttle body bore. On older models, sometimes someone would “adjust” this screw to “adjust” the idle speed and end up making it look like the driver still had their foot on the pedal to the TPS. When conditions changed, like temp or barometric pressure, the idle would change, sometime too low to keep the engine alive. There would be no code or CEL (check engine light) because the PCM did not know that the screw had been changed. I’m not sure if someone fiddling with this screw would have the same effect on fly by wire throttles.