I Have A Tall Ceiling, Should I Use 2 Or 4 Height Speakers?

As always: It depends

If you have a small, but tall, room; 2 height speakers are usually enough. If you cram 4 height speakers into a small space, it will affect channel separation and the end result can end up being muddier than wanted.

If you have an overall large room and you're able to space the speakers out, 4 speakers can sound better, and especially overhead panning-effects can sound more enveloping.