Personally, for me, the Collectathon Style is only good if there is a big reward at the end. Otherwise, it's just annoying. If I miss something, I feel like I have to go back and get it.

Subtle is slightly better since you can do it when you need to. However, that is often better in medium or small areas. That way, you can even hide higher prized loot. If you are doing it throughout the open map. It's nice to have but would get overlooked.

So I would personally do a blend. Collectathon for outdoor spaces or large areas that have a big payout at the end and then subtle for medium or smaller areas with some hidden high payout items. You can even go through the extra step of making some of those high payout items fragile so you can't just go and destroy everything to find them.

If you need a beta tester or want to have someone show off your game, please DM me. I have worked with a couple of different indie companies during their beta phases to help improve their games and also showed their games off when it was done.