Is there any brand copoly that "sinks" like fluoro?

No, there isn't any nylon or copolymer line that sinks as fast as pure fluorocarbon.

The fastest sinking copolymer lines are those that incorporate some fluorocarbon.

For example, "P-Line CX Premium" is a nylon copolymer line with a fluorocarbon jacket.

 

Be wary of the consensus.

Although braided line may float it possesses a much thinner diameter, 

and that throws a big monkey wrench into the equation   

 

Roger