Mod's to suite vehicle usage

[T'subaru]

Hi guy's,
After reading brumbyrunners recent post in wheels and tires I have a few questions that may be helpful to all less knowledgable mod planners like me, a subi-newbie.
Vehicle: '89 RX ea82t 5 speed awd
On road usage: Daily driver to work, 300 miles a day freeway ( 3800 rpm at 110 kph)
Off road usage: ocean beaches, snow and ice winter commute.

Ultimate Goal:In my case I'm going for bling! I want tire width, along with a bit lower top end rpm. I would like to run 8 to 10" wide rims ( I can open up my wheel wells on the rx much more than my loyales) with the ultimate goal of driving a really unique vehicle.
Is there a formula a person can use based on final drive ratios, tire sizes etc to best suit vehicle mods to vehicle usage?
Cheers