There isn't an easy answer I don't think. Some will depend on where you're going, what the luggage handlers are like ( I don't know anyone that's had anything stolen from their room, but I do know a couple of people who've had stuff taken from luggage), what the location is like and the type of accommodation you're in. For instance, I'd feel safer in an apartment/Air B&B than I would in a hotel. Just feels like there are fewer people in your room on a regular basis. I have no stats or basis for that btw.
I took the best kit I had available to Cuba as I thought I might get some good/interesting shots there. But I did ask the question before I went as to what it's like because I was concerned.
And once I moved to FF, I did keep my crop sensor camera for a while with a view to taking it on holidays, as it was smaller. But to be honest, it wasn't so much smaller it made THAT much difference and then raised the question of why not just take the big one? So I sold that and got a bridge camera. Which is mostly great, but does struggle at times with a 1" sensor.
And in almost every instance, I have a smaller compact which I take for nights out. Therefore leaving the 'big' camera in the room. Perfectly acceptable for the type of shots you're likely to take. Not as good as a FF camera, but way better than an iPhone.
I've never put one in a safe, and I've never had any issues. Maybe I've been lucky.
The last time I went abroad was to New York. I'd been before several times and wanted to try something different, so took an old film camera and lenses and also a MKI Sony A7 to pair the film lenses with. They're probably some of my favourites shots. and the entire camera and several lenses cost less than just one
second hand L lens.
I'm going away next month and will probably replicate that set up again. It is still a FF camera, but paired with older Minolta lenses is very small.