If you choose a trailer, look for one that is nearly as wide as the van.
Do not get one with wheels that are wider than the trailer: although that makes them slightly more stable, it makes manoeuvring a nightmare.
Try to get a trailer with straight sides, so you can easily see where it is pointing.
As already said, the longer the trailer, the easier it is to reverse. However, the length that matters is from the hitch to the axle. The rear overhang is unhelpful.
If it is a very small, light trailer, you could have the axle near the back. But unless it's a very light trailer, the hitch can get very heavy very quickly.
I would install a reversing camera, wired to be on whenever you switch the ignition on, not just when reversing. That's what I have, even without a trailer!
And then spend some time practicing reversing. Backing into supermarket car park spaces is a good way to get the hang of it (when the car park is empty, of course).
You should have plenty of time to think about this now.