It really depends on the bunny , my two cope fine with once a week 45min car trip (the rabbit savvy vet is that far from me and I’ve had to go once a week to once a fortnight for treatments lately plus vaccinations and neuter assessments etc )
You won’t really know how stressful they find the car ride until you have had them in the car – maybe you could go through a rescue where you can ask what they were like on transporting there , trial a short car trip each with the ones you are looking to adopt and see who cares and who doesn’t mind the car ride
Or perhaps look at a bonded pair as they would comfort each other on the journey ( would need to be neutered / spayed already and pre bonded as you would have to wait approx 5 months before you could look at attempting bonding once both a spayed so doesn’t help you in the meantime )
Keep as much the same as possible – have the same setup at each house as far as litter tray set up , indoor cage ( if you have one or “area” with bed / hideaway etc if you are going to free range )
Take his/her/their things with their scent on them like blankets , soft toy , bowls with you between houses so their is always familiarity and I would have the carrier you will use for transporting out at all times open for them to go in and out of so it’s a safety place for them not a place they associate only with the car
I think if you have the time for a bunny to have 4-6hours out a day ( usually split between dusk and dawn although mine are active from 6pm- 12pm so they are out then ) , can provide what they need , I wouldn’t let the car ride out you off
just as I said a rescue may be the way to go as you can discuss this with people ( at the rescue) you know well the particular bunnies you consider. And there is generally more flexibility to trial things ( as They cater play dates for people looking for a friend for current rabbits) so I’m sure you could arrange to trial a car ride with the ones you are interested in