Sorry, I don't know of a way to turn off the nightlight feature without using the app. TMK, app is also required to turn off unwanted modes (e.g. strobe, SOS, etc.), set auto-off timer, and set low battery warning threshold.
It seems that way unfortunately, you really do need the app to have true control over these lights.
For me the most important aspect is to reduce excessive parasitic drain. This means turning off the RF and flashing of the side switch. Now I've been able to play with the app a bit on a borrowed ipad, I've found the following:
The side switch will only stop flashing if you are in the settings page for the light (with RF on) and then turn the RF off using the ten taps.
-if you toggle the RF at any other time, it starts the side switch flashing again.
When turning the light off, the side switch stays on for 60s. To stop this you must use the app and set the nightlight setting to 0s (it was already off).
So now I've got the two lights setup as I want, I just hope they don't reset and go back to default. If they do, I'll need the app again. We also don't know how long that app will stay in the app store as the new management might get rid of it.
A real pity it is so app dependant and iphone exclusive for the finer details. These have a lot of potential.