Starting EV tariff before EV charger arrives

Hi,

This is a bit of an odd question - but I'm new to the EV space.

I'm on EON Next Pledge tracker dual fuel tariff due to end mid August. Then it would switch automatically to a Variable Tariff.

My EV and EV charger will arrive around mid September.

Would it make sense to switch to EDF's Go Electric in mid August just before my usual tariff ends?

And with these EV tariffs do U specifically have to use the EV charger during the off peak (as in do they specifically measure the EV charger being used?)

Or would it be better to just switch to an EV tariff once the car and charger are installed?