Two things: the MOST IMPORTANT one is that you're highly unlikely to have any problem at all, especially if you're not staying in big cities; the second is that if a thief has tools and time to use them, they will have your bike. Mobile security is about making it more trouble than its worth, but your best defense is always not having a thief know the bike is there.
So the main thing is not parking with the bike on display: if booking ahead, I always email the hotel and ask for secure parking for the bike; most reply to say they have a courtyard or a garage or somewhere secure where I can park it at the back of the hotel. Certainly, if a hotel's details say it doesn't have private parking, I don't book it. If I'm just booking as I go along (4pm, look at the Booking app to find possible hotels about 2 hours ahead), I phone the hotel and ask about parking before committing to staying there.
Even so, I do take a lightweight chain (the current version is
this) for the back wheel or for grouping upto three bikes together, and an alarmed disc lock for front wheel (I use
this one). They've never been needed, I don't think, but I have them so it seems stupid not to use them.
When chaining the bike up, it's important not to leave the chain or lock lying on the floor, where it can be smashed with a big hammer. Ideally you'll chain it to a solid object (a fence post or lamppost) so it's suspended. If there's nothing to chain it to, try to loop the chain up around footrest hangers over the tail in such a way that it can't be freed and dropped to the floor without unlocking it.
And if you're taking a chain, do take a chain. Any set of bolt croppers will go through armoured cables in seconds. They may not take much longer to go through a thin chain (maybe a minute or two), but a big set of bolt croppers will make mincemeat of even thick cable. However, I wouldn't take a big, heavy chain - there are really good, uncroppable, practically indestructable chains from the likes of Pragmasis and Almax, but they're just far too big and heavy for touring. Great for the garage at home, no use on the road.
But frankly, unless you're leaving the bike unsupervised in the Paris housing projects, it's all likely to be overkill. How many people on this site have been touring for how many years without problems? You have to say it's the equivalent of several years of being on the road over there non-stop. You'll be fine. Just park sensibly.
D
