太…了【tài … le】

太…了 says something has gone past the acceptable point. The 了 is part of the pattern and is not usually left out.

Also as an exclamation

With a positive adjective it stops meaning "too much" and becomes admiration.

Context decides. 太大了 about a room being viewed is a complaint; about a portion of food, it could be either.

不太 for softening

不太 does not mean "not too much" – it is a polite way of saying "not very", and it is how a speaker avoids a blunt negative.

不太好 is a gentle way of saying something is bad.

No 了 with 不太

bù不tài太Lěng冷le了 is wrong. The 了 belongs to the affirmative pattern only.