Each Collector Booster includes 1113 Traditional Foil cards
Flashback cards have the flashback keyword ability, which is only found on two card types, instants and sorceries
Most Magic sets have alternate art these days, often with special frames that help exhibit some of the set's influences
A higher amount of Dragons than Knights seems better with your two Commanders because double strike with Dragons who already fly is more powerful then Knights with flying
Adding creatures and instants that are able to blink allows very simple ETB retriggers, and with the commander, you can get a ton of extra retriggers of key abilities, such as drawing cards or creating various Tokens
For example, a counterspell is usually seen as a mean card