Pontoon design and level sitting angle

A newbie on the line....

After noticing most pontoon boats sitting low in the aft section, due no doubt to the porpulsion unit; is this sloppy design work or simply a matter of money and ease of construction?

More to the point.... is it even desirable to have a "level" sitting and running pontoon boat? If yes, which would be the better way of handling the problem, adding a thrid pontoon to the aft section, or adjusting the size and design of the pontoon log as it goes aft?

One other question, cost aside, would it be more or less desirable to have an outboard on each pontoon log versus one in the middle?

Cheers, Bill