It really depends on how much you have to spend and what you can lift. For me having a Team Hybrid Cougar rebuild put on my old Powertrike worked well so i would say the Viper wheelchair attachment is worth a look. It is £3000 new
https://www.teamhybrid.co.uk/product/viper-sport-power-cycle/, and you would need a rigid wheelchair to attach it to. I already had the chair which I got using a wheelchair voucher combined with some of my cash money to get a Bromakin Titanium lightweight chair. The wheelchair is markedly heavier once the attachment port for the Viper is fitted, but I was able to manage it on my own on and off for several years. I used to get offers of help from random people in car parks some who were able to help and others that got the Viper in the boot badly hmmm. It was nice to have someone trying to help though.
I dont know much about trikes or scooters but have looked into the options from time to time and the scooters that can cope better in the countryside cant be just lifted into a boot, this means a wheelchair accessible vehicle is needed.
I few years back I had to cut my motability contract short because Bran gre big quickly and there was not room in that car for three dogs, two humans, a wheelchair and Viper attachment. We now have a Citreon Berlingo.