The only Normal Monsters to be restricted are the four limbs of the Forbidden One, which are all Limited, and the Match winners "Leonardo's Silver Skyship", "Sakyo, Swordmaster of the Far East", and "Shelga, the Tri-Warlord", which are Illegal
OP-16 Sakazuki (Akainu), by contrast, combines that same IP prestige with genuine competitive relevance in Sengoku's Navy deck, which is part of why it currently outprices the other two Admirals
Her I Trust You ability lets a player look at the top two cards of a deck and take one into their hand every time she quests, generating plenty of card draw and making it easier to get a specific target
K9 - Lupus, meanwhile, is a special case in that his form of self-special summon is reliant on the opponent activating a monster effect from either hand or graveyard