tidus card sleeves Magic: The Gathering®—FINAL FANTASY™ Tidus, Yuna's Guardian (Commander) 100ct DECK PROTECTOR® Cheer — Whenever one or more creatures you control with counters on them deal combat damage to a player Official FF Magic Sleeves Washing

Too few lands and the player will have great hands full of spells but no land with which to bring them in to play (this is known as being "mana screwed") whilst too many lands means the player is able to play lots of spells but their chances of drawing them is lessened (this is known as being "mana flooded.") This is further compounded by the effectiveness (or power) of a card being designed to correlate with its mana cost (or how many lands must be used to cast the spell)

Usually the latter

Can you cover every card from a set : Potentially every card from particular sets in the future but definitely not every set and card due to the time it takes to collate the information

The Goat Format Europe discord server often runs tournaments with special rulesets named Slifer Specials, which has now become a bi-monthly series