2x chance actually gives you double the chance to pull an epic or legendary from an ancient/void shard, or a legendary from a sacred shard, during their respective events.
10x chance DOES NOT increase those odds, at all. It only increases the chance that IF you would pull an epic/legendary from an ancient/void/sacred, there is a 10x higher chance that you'd pull one of the selected champions, than that you'd pull anybody else. Although considering the number of champions involved, that still leaves you with a relatively low chance of pulling the champions in question.
Hence, for newer players, it's recommended to ignore 10x events and pull your shards during 2x - because you don't have many top champions yet, so you'd rather have a higher chance of getting any epic/legendary. A possible exception is 10x events in which a very good non-void epic is offered - then you might consider to try pulling some sacreds and hope that you'll get the selected epic (with still a small chance of getting a lego instead).