I'll stick with the technical side of things. Getting yourself set up like you want isn't that difficult or super expensive. So let's get into it!
First thing you'll want to get is a USB hub. If you have a USB C connection on your laptop that would be the preferred connection. This will allow you to have your monitor and other computer items hooked up constantly for backseat use. When I used to take my laptop home from work I had a hub connected to keyboard and mouse, monitor, printers, and whatever else I needed in the office. When I went home I unplugged the hub and went home. Move to the back and plug in the hub. Easy peasy.
USB C Hub, QGeeM USB C to HDMI Multiport Adapter 4k, 7 in 1 USB C Dongle with 100W Power Delivery,3 USB 3.0 Ports, SD/TF Card Reader, Compatible with MacBook Ipad HP Dell XPS and More Type C Device
https://a.co/d/c7vdgV0
You'll need a way to mount your monitor so it's out of the way, but accessible when you need it. This isn't a bad mounting option. Has good reviews and it's simple and removable later. There are other options, but most will involve more work and possible expense.
All Sturdy Aluminum Alloy Metal Short Length Type TV/Monitor headrest Mount Bracket with a Steel Plate That has 75 & 100mm VESA Standard Holes
https://a.co/d/cqpXbpq
When you're up front and need to use the laptop, you need an easy way to use it. This mount requires loosening one bolt to attach it.
Mobotron MS-526 Heavy-duty Car VAN SUV iPad Laptop Mount Stand Holder
https://a.co/d/gQFZFn2
Having a wireless keyboard and mouse will be essential to moving around in the van. If you have one already then that's great. If not, here's a cheap but solid unit. You can also set up your laptop to work with the lid closed. So you can have it closed somewhere just plugged into power and the hub. Takes up less space.
Logitech MK345 Wireless Combo Full-Sized Keyboard with Palm Rest and Comfortable Right-Handed Mouse, 2.4 GHz Wireless USB Receiver, Compatible with PC, Laptop
https://a.co/d/fmykCmQ
When working in back you'll need a good workspace. This lap desk can hold your keyboard and mouse, as well as some papers if need be. It can also be used as a utility board of sorts. Meal prep, cutting board, whatever you might need a convenient flat surface for. Definitely multi use that can be stored out of the way.
32" Portable Curved Shape Light Wood Lap Desk by Trademark Innovations
https://a.co/d/g6LWi4D
You'll want to use a 12v laptop charger when you're on the road. Using a 120v ac adapter is just wasting energy.
LVSUN Universal Laptop Charger 90W 12-24V One for All - Slim AC Adapter Power Supply Cord with Dual USB Ports for Mobile/Tablet - Compatible with Lenovo HP Toshiba Samsung Acer Asus and Most Notebooks
https://a.co/d/j0iXEEN
If you have specific questions let me know. This is kinda my wheelhouse. Also see about getting a 12v adapter for the monitor as well. Again, it'll save energy and these things already work on DC.