I'm not sure that trend holds. Most banking apps let you send tens of thousands in one go. They're very aggressive with the "are you sure?" question in my experience though.

Yes mine let's me put in a limit. I have set it to a low €500 since I rarely do large purchases in webshops.

At the end of the day people are responsible for not doing business with shady stores or people. But the idea that a single QR code can empty my entire account is sobering...

Yes if you are dealing in small amounts that you wouldn't mind losing to fraudulent apps, then do it, but read my previous comment about locked down machines if dealing with very large transactions.