Is this important data or just digital hording? That's probably the most important aspect to think about. It sounds to me like it's the latter. Stuff that you like to have but if it was lost, it's not the family photos our other irreplaceable data.

For that USB raid, or even more is drives are fine. The problem may be how often do you want access. If it's something constantly available then maybe a small home nas might be a better option.

I don't have any recommendations for a product, but something to be cautious about with things like raid 5/6. Cheap appliances are cheap for a reason, and double/triple drive failures are known to happen. Spinning rust is pretty cheap, so it might be something you want to keep multiple copies of sitting on the shelf.