Help about a camera and a USB microphone

[RandomMike]

I think I've found a nice camera : Canon Vixia HF R500 with a mic input. But I have some worries before purchase :
Why is it cheaper than the HF R400 even though it's newer, is it worse in quality / maybe it's delicate or something?
Is it safe to buy a used one in a good condition? Or these cameras are too fragile and maybe it's been damaged and will break soon?

What do you think of a GoPro as a YouTube camera? (It doesn't have a display - so maybe there is another way to see what you're currently filming)

Go pros are good if your doing a lot of action but cost a lot. And back to the canon have a look arround and read reviews what people have said thats the best way to decide in my opinion.