Reactor & "My Modes"

I’m new to reactor. I have followed the instructions and worked out how to install and configure Reactor.

Until now I have been using “my modes” to arm sensors in away mode and to trigger alarm devices when the sensors trip. I have one external movement sensor on a camera which I leave unarmed, because I don’t want the alarm devices to trigger when someone comes to the front door.

Recently someone suggested to me that I could use the “armed” status of devices more ingeniously by using a reactor sensor to arm the exterior movement sensor at night, and create a scene that turns a light on and off only when the external movement sensor is armed and triggered.

That appears to conflict with “my modes” which triggers the alarm devices when any armed sensor triggers, so if I enable my reactor sensor someone coming to the door at night in away mode would set off the alarm (undesirable).

It seems that maybe I have hit a tipping point, where if I automate certain functions with reactor I have to go all-in and stop using ‘my modes’ and replace it with more custom automation.

Am I thinking the right way here? Should I disable all the logic in “my modes” and replace it with (a) a reactor that arms sensors in away mode and (b) a reactor that triggers the alarm devices when any sensor except the external movement sensor fires?

Grateful for any guidance.