My favorite Historical SP total war Lets Player is OfficiallyDevin, who really goes the extra mile. His Narrative let's plays (which he invented and others copycat to varying success), are like watching a show. He creates cut-scenes, voice acts them, gives the characters personality. He edits his videos, using replay footage when possible to get good visuals, and ties all the game-play together with a clever meta-narrative. Each one has its own tone, great ones to start with are Massalia Tales (DEI), Barbarian Masters (Shogun2), and Fields of Mars (Attila). Some of his Total War let's plays are zany comedy and not representative, so beware. https://www.youtube.com/user/OfficiallyDevin/playlists?shelf_id=7&view=50&sort=dd

My favorite Fantasy let's player is SurrealBeliefs. He really has fun playing and you can see that in his enthusiasm for discussing his strategies. His commentary keeps things from ever getting boring, honestly I could just listen to his let's plays as a podcast and still get entertained. His channel is the best way to get to know old Total War mods like Call of Warhammer, Third Age. Mostly does warhammer now. https://www.youtube.com/user/Surrealbeliefs/playlists?view=50&flow=grid&shelf_id=221