I have a number of Blink Mini Indoor and Outdoor cameras in a variety of locations so here are my thoughts. Blink Indoor cameras are good but.... they are sensitive to changes of light and also attract insects, so the one in my living room goes off when the bin lorry goes past with flashing lights at 7am, and the one in my shed is frequently activated by spiders and wasps crawling all over the lens, so actually they're not really appropriate for a van setting with car headlights going past all the time. I would recommend the Blink wireless camera because it is a camera triggered by a PIR sensor so is impervious to passing traffic. Just for the sake of clarity, there are indoor wired (from a power perspective) and wireless version with 2 disposable 1.5v lithium batteries, and a wireless outdoor version again wihtt he 1.5v lithium batteries.
I use the recommended Blink Sync Module 2 which reduces the power consumption of the Wifi sensor as it uses a lower power network for control and only WiFi when sending video. My wireless camera is an outdoor one and can be run via the micro USB socket on the back (as can the indoor plug in version obviously). I'm not sure whether the wireless indoor camera has a micro usb socket or not though. I made some measurements this morning and found that the Blink Indoor camera takes 50mA quiescent and 150mA when streaming video. However, the Outdoor quiescent current doesn't even register on my USB in line current monitor, but jumps up to 80-100mA when streaming video.
So in summary I would say the Wireless Blink is a much better bet for a van. You still need a Wifi network of course, but if your van is within range of your home network then obviously that's ok. If you want to site a router specifically for the van then you might want to consider this wifi extender which either acts as an extender or can create it's own network by plugging it into the ethernet port on your home router. It has a higher power setting which can be set up, although I'm not quite sure how that might conform to the permitted maximum power levels.
https://www.amazon.co.uk/gp/product/B0B1Q1HDNL/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1. Otherwise, a MiFi-type device would be needed, which might possibly cause excessive battery drain over time.
Hope that sheds a little light on things!