I can help with a few:
> Weight is also important as it will go on the back of a VW camper on the rack
Take the battery+motor unit off first, and pop it in the van. That's 3-4 Kg saved.
> Will it be OK on a bike rack in the rain for say 4 days as I travel? (Will the electrics be safe?)
Ah. If you take the battery off and then drive in spray, water will get into the battery compartment. You'll need to dry the compartment out (kitchen roll or similar would do). The majority of the water will drain away, and the connector is on the top edge of the compartment, by design - see pic 1 where I tipped about 100ml into it. I dabbed out the small pool that remained easily.
The alternative is the leave the battery in, which gives less holes for water to get in. The good news is that battery+motor removable unit has a small drain hole to allow any water getting in to exit again. You'll want to:
1) make sure the drain hole is clean/open before mounting the bike on the rack (or any time you ride in a downpour too)
2) remove the battery and have a look to see if any water remains inside. If so dry it out with kitchen roll/tissue.
https://fazua.com/en/magazine/bad-weather-check/?from=inside-fazua
One last angle, possibly the smartest one, is to buy a 'dummy' battery cover - it's replaces the battery+motor, and is like an empty shell. About £60-70:
https://fazua.com/en/drive-system/evation/downtube-cover/
> Does the Boardman not have fast release wheels? Issue?
An allen key is needed, so not a big issue, since that goes into an small under-saddle tool bag easily. See pic 2.