If you are looking for an extremely fast flatwater board with maximum glide and stability, surfing paddle board is the one for you. this is possibly the lightest, strongest and fastest flat water race boards around.
It's an incredibly fast shape, and it's really stable for its size. You will be able to go less wide than what you think - it was designed to be stable enough to ride super skinny.
Surfing paddle board are great for all open water, flat water, or downwind environments. The board is going to be longer and skinnier than something like an All Around SUP and it will have a displacement hull which both result in a reduced amount of drag. The shapes of these boards is no happenstance- they are developed, tested, and analyzed in actual race or downwind environments to find the right shape to make them rocket fast.