Since the most cards you can draw in a turn is 5,

What happens if you draw 4 or 5 cards before the draw phase?

A clarification; the "Draw cap" is actually only a cap on the number cards you can draw in addition to the framework draw (and this is limited to effects that actually use the word draw, not simply "put in your hand" etc), not the total number of cards you can draw. While certain game effects modify the draw cap (eg; Dolorous Edd, Song of Summer, Rotten Bastard), what this means in the vast majority of cases is that you can only draw 3 cards a turn plus your framework draw (which is normally 2, modified to 3 by the melee title "Master of Laws"). That's not exactly the same thing as saying "you can only draw 5 cards".

So for the short answer to your question; "Normally, you can't".

oh ok cause I was mostly wondering what would happen if I used King's Landing at the start of the Plot Phase to draw a card and then Used Threat from the East.

So in this case I would draw one from King's Landing but only draw 2 cards from Threat from the East then?

Correct.

Said another way, you CAN'T draw 4 or 5 cards before the draw phase using card effects because you are limited to 3 by the cap.

Well since I already have a topic about draw, does TLV count towards your three card extra draw?

Yes. It is a card effect that uses the word "draw." As per the FAQ, any card effect that uses the word "draw" counts toward the draw cap.