Thin stretchy carpet is
Thin stretchy carpet is better to mould around the corners in the van. The cheap stuff from carpet shops, which is generally foamed back, is thicker and insulates better, but is hard to mould around the corners.
The easiest and cheapest way is to buy a tent hookup connector. Most campsites are fine with you using this.
Electric are fairly straightforward. One just needs to understand the rules before starting.