Realistically getting a sail for 30+knots is pointless (says the man with a 5.1 race sail

).
For here a 58 wide board you will get a fair amount of use out of. Sail wise a 6.0 will see you for 20-30 knots, if you chase the flat water you could hold it in more than that if required.
Fin wise look to something around 31cm for chop and 27cm for the flat.
You could easy go smaller with board, sail and fin but you don't just buy something and go super quick on it. Going quick is very dependant upon how much you use, how well you know your gear & how easy it sails.
If you wanted to focus straight away the ideal FLAT water speed setup for seq as much as I hate to say it- CA speed 50 (unfortunately no other brand offers something of similar width vs volume), 6.3m race sail (maui, naish, loft or pryde).