Angels is a tribal synergy deck. It benefits from the interactions between Bishop of Wings, Righteous Valkyrie and Resplendent Angel. While decks built around life gain have historically not been the most powerful thing to do in Constructed Magic, this deck plays to the board, can go wide with Resplendent Angel making free tokens as soon as turn three and the buff from Righteous Valkyrie makes it pretty easy to overrun the opponent quickly.

Angels is a fine deck to play in the Best-of-Three format and I would currently rank it around top five in the Explorer Power Rankings, but it’s a lot stronger in Best-of-One. The reason for this is that you heavily rely on all your Angel synergies and need to always keep a high creature count for Collected Company. If cards like Scavenging Ooze had the creature type Angel, it would be easy to heavily improve your deck after sideboard against specific strategies, but that’s unfortunately not the case. Your deck also has no card selection, so even if you bring in four Rest in Peace for a matchup like Greasefang, you can easily end up drawing one or two redundant copies and effectively take a couple of mulligans. It will also lower your creature count, so you will be less likely to hit with Company and so on. 

This is roughly what a traditional build of Bant Angels looks like.