Combat system spoilers I guess, obviously nothing plot here but I know some people don't want anything.
Later in the game it look like you will unlock a a second set of Artes slot by holding RT/R2 in combat, bring your total Artes on a character to 12 instead of 6 like the demo had. Probably explains why default normal attack is R1/RB. The small number of Artes your character could have was a big worry for me, so this is good to hear.