Speed suit v. Wetsuit

A wetsuit is generally made of neoprene and offers flotation and a bit extra thickness (which increases arm/leg surface, therefore you have bigger "paddles" that you're pulling and kicking with). This makes you go significantly faster.

A speedsuit is more like a swimsuit on steroids. They are often tri-suit or full-body suit shaped; the material repels water and so "slips" you through the water faster by decreasing friction of water against skin or material. But they are not flotative nor do they add any thickness.

No, the speedsuit is stripped off at T1 like a wetsuit. No padding/chamois.

As for the non-buoyancy, there is actually some additional "buoyancy" afforded, in that the material doesn't soak up any water, thereby giving more "floatation" than a regular tri suit.