I am 5'10" and 12st 5lb also. I have an orange street triple R with both the Fly Screen Kit and Fly Screen Visor Kit. I have ridden different bikes without the fly screen (i.e. Ducati monster 696) and reckon that it defiantly makes a difference. I recently worked out that if you duck under the fly screen you can get an extra 3-6 mph by reducing the wind resistance.
I also use my bike for commuting however I use a rucksack to carry my clothes and shoes (don’t forget your shoes incidentally!

) and don’t have any problems with the added weight on my back.
I don't notice any buffeting at 70 mph (only when it's real windy or overtaking large trucks). There is allot of wind at 70 mph which can be a bit loud in the "skid lid" and tiresome to travel long distances in, but generally it’s a numb butt as opposed to a sore neck that most people notice when on the triple for any sustained period. I have never suffered from a sore neck, and I have ridden my bike for 5 hours at a time on occasions, stopping for the odd for refuel.
There are tank bags and other storage options available, but I have no experience of these, sorry!
It is a whole load of fun to drive and will leave you grinning from ear to ear, so good luck with your decision, either way!