I have done a lot of touring on bikes in cars and trucks.
In France you need to understand that in some places the right has the priority, sometimes it is signposted, other times it may not be.https://www.france-pub.com/forum/2012/04/14/la-priorite-a-droite%E2%80%8E-priority-to-the-right/
However, the rule of thumb is that the larger vehicle is usually liable, if an accident does occur, not always good if you are on the floor with broken bones....I have had a couple of accidents in France and Belgium, one which required hospital and emergency services, they knocked spots of the UK.
Spain, if you do not have the correct documentation they will fine you on the spot, they are usually total twats as well and take no nonsense....This is the National and Civil Police, the locals, like the French Gendarmes are good usually.
I have not used a GB sticker on a bike for years and never bother with any of the other faff, however, if you are driving at night, you will need to use a bit of tape to divert your hi beam, this year I came through spain and france in the dark and they were not happy bunnies, I had to buy some tape and it stopped the flashes.
I have been stopped by the Police in all countries for all kinds of traffic offences, each time I have used distraction to get off the ticket, each time it has worked
Just being nice and flustered and usually lost does it for them and they want to help you then
I have never had any problems with security of the bike, usually you are looked after by the hotel owner etc. I have left bikes in market squares over night, never a problem.
All in all I prefer and do more miles a year in France, Spain and now Portugal and it is such a breath of fresh air to be amongst people who actually know you are there and do not suffer from this small penis syndrome that affects many Brits.
Enjoy, the beer is better and cheaper, the food is better and cheaper and so are the hotels
Wine.....Well, what can you say.