Well, Dynasty Warriors follows Romance of the Three Kingdoms, which isn't even history. RotK is mysticism and a tall tales of historical Chinese figures. Records of the Three Kindgoms is the historical document. Dynasty Warriors is just straight up RotK fan service.
As for the spin offs, Samurai Warriors DOES follow history, but in a more - again - mystical and tall tale way. It's still fan service. Tales say Oda Nobunaga was a demon, so they have his sword be a fucking lightsaber and shit.
A big part of the appeal of any Dynasty Warriors game is "getting" the source material, whether it's Gundam (animu), One Piece (animu), Fist of the North Star (animu), Sengoku era Japan (animu history), or Romance of the Three Kingdoms (animu history).
It's like if a western studio made a beat em up rts game about the American Colonists fighting the British Army. Instead of fighting like normal, you have George Washington killing dudes with a surfer board, or Bejnamin Franklin killing people with his giant weed pipe. Shit is hilarious if you get the references.