Unfortunately, there is no general answer to this question. As far as I have found out, there are accessories that are compatible with both versions (e.g. all-purpose tripod, Bullet Time Cord) - but there are also accessories that are specifically designed for the products mentioned (e.g. battery/charging station for One X2).

All accessories for the desired version can be filtered on the manufacturer's website. There, it is usually already mentioned in the title with which cam / which cams it is compatible. I hope that I was able to help you with this.