You can use the exemption on a second car if one is an EV as they’re exempt.
You can also choose to pay the road tax on your motability car if it means saving money on the car you own.
For example I keep the exemption on my Grand Voyager as its £450 a year as my MG ZS EV is exempt and its all worked perfectly no bother.
And before anyone has a go at me the GV is for when we need 7 seats or to tow a caravan it doesn’t mean I’m rich thx