Boxed copies of games with Steam keys - region locked?

https://steamdb.info/app/337000/subs/ shows a lot of different regions with cross-region trading not allowed at least.

play it safe and create a region-locked GA?
Or just state in the text that people agree if it is region-locked to give up their win

I know of region locked keys, and while those in HumbleBundle are most well known, that system is actually set up for retail distributors across the world. Not sure about those particular boxes but probably.

You can ask the publisher. Here's a discussion on the Square-Enix/Eidos forums from six year ago that had official confirmation that DE:HR box copies were not region locked, at least for the regions mentioned and at that time. Here's the DE:MD forum. I didn't see anyone ask that already, but you can make a post there or check the box itself for contact information (email or toll-free number).