No you won't..

Flashing an XT vbios to a non XT card is the only thing that is possible.

The onboard PSP prevents you from doing modifications.

Also, memory timing changes on a Navi are like on an R7, useless.

The only thing that would improve performance (particularly eth mining wise) would be to make it so that you extend your bandwith.
Which means that you would need to change clocks + timings so it remains stable and because the PSP on board even has it's own PPtable, this is yet again not possible.

Well, anything is possible, or almost :p
But at this stage, i doubt anyone has been able to accomplish vbios edits for navi (basically bypass PSP).

Cheers