I find it easier to think of the 2 this way.
Carb ratio is a calculation to determine how much insulin you will need not the meal you are about to eat. If you enter your carbs and it suggests the right amount of insulin then you have a good ratio set up.
The sensitivity factor is what your pump uses to do it’s own bolus corrections and how it determines your basal rate from min to min.
So really your carb ratio does very little. You can alter that before you deliver anyway.
So if I’m eating and it says will deliver 2 units. I might say no way I need 3 and you can change it to 3. But then you should look into altering it. Just for ease of use.
Sensitivity factor is where it is at for control iq. But you need to make small adjustments so you don’t start going too low.
Best time to look is at night in sleep mode. Fewer variables.
Correction factor is the same thing in tandem.