Mine was all pretty straightforward and was sorted fairly quickly. Not sure of exact timelines tbh.
Power NI have the only EV tariff and you would need to do the maths to see if it works for you. Cheaper night rate and more expensive day rate. Mine started at 12p a kw but is now 18p. I ain’t looked in a while but believe it’s still works out better for me.
You need a separate unit for the EV tariff as one counts your day kw and one your night kws so if you are pay as you go you can’t get it without going DD.