Based on my XL Berlingo:
Rear row leave small holes in the floor when removed, so effectively flat floor.
Middle seats independently fold flat, kind of concertina-ing into each footwell. So no problem to have any two up in the second row with one to added as fifth seat in rear.
Not encountered AdBlue issues in the three years we’ve had ours, FB groups I’m on suggest there are people who will map it out if that’s the path you want to take, no experience of the petrol in terms of viability with a fully laden car/van.
Can fit my enduro 29er in the back with rear seat out and one middle row seat flat, just wheeled straight in.