The 920XT is a step forwards from the 910 when it comes to pool usage.
It does all that the 910 used to do PLUS it allows you to record/highlight DRILLS and to have more control over your REST INTERVALS.
It’s a bit tricky to use first time. It’s NOT intuitive. Well not to me. But it is fine once you have the hang of it.
It’s probably best to watch this nice short video rather than reading the manual. It’s good and fairly short.