Tire Size and FE question

[GMKing]

I've got quite some time before I need new tires, but that just means more time to save up for some good stuff,

before I begin trying to plan which tires and wheels I want I was wondering how exactly does tire size (both height and width) effect FE?

example, if I go with a taller than stock then my acceleration should decrease but my top speed should increase, which means that the revolutions of the engine are each individually pushing the vehicle just a bit further due to greater tire size.

if I go with a smaller tire than the converse is true. however, the engine techinically needs to work harder to move the taller tire than the smaller tire, so I'm wondering where does FE fall in? taller tire and greater FE or smaller?

also, width of the tire, I can only imagine that going wider increases drag both from air resistance and creating a wider contact patch and therefor increases rolling resistance. but I might be wrong.

as for the rims, my only plan is to stay with 15's or maybe go to 16's but no more, and to obtain the lightest set possible cause low unsprung weight is good good good. Thanks for all input