Weapon changing is basically up to you. Each weapon type has a particular battle style, so knives will be super quick, great swords will be very strong but much slower and combo poorly, while spears are great for reaching fliers. Enemies also have weaknesses and resistances towards types of physical damage so be on the lookout for that - the game tells you whether they’re weak resistant or neutral via the color of the damage numbers, but I don’t remember which color meant which

Honestly, the battle system doesn’t really get much more complicated than that, but what I really loved about it is how relaxing it is. Holding the buttons is a great alternative to the usual button smashing in action RPGs and it always just felt really fluid once you get into the flow of combat.