To add to CW's comments, the searches often bring up interesting comments and perspectives about your topics that you may otherwise not see. The best advice I've read on any forum is to let your needs dictate your modifications. Don't go crazy pimping out the bike all at once, but when you have a need or something bothers you, make changes or add things to address that.
You are commuting now, the size of the top box is dictated by what you need to carry to work and back on a regular basis. Many top boxes are quickly removable w/o tools, or can have that option. Allowing a fast swap from one size to another if multiple sizes meet your needs for commute Vs Touring.
Holan, Touratech Zega, SW Motech,
Bumot,
Happy Trails,
Tusk,
Givi and many, many more options out there for top boxes and side cases/bags.
Many racks allow for quick, tool-less removal of the side bags. (
Zega Pro in my case) The pannier racks do not really add any significant width to the bike, and give you some side protection for the bike in urban assault riding. That said, some love the
SWMotech rack's ability to quickly remove the racks too, and the asthetics that allows when there is no need for side bags. Givi offers a quick release side case frame now too.
In reality, anything narrower than the handlebars is going to go thru the 'hole' you find in traffic. That said, it's un-nerving to catch a bag on a solid object when working the bike back and forth.
Hard side bags or soft? For off pavement, many people prefer soft. For your planned Alaska trip, (BTDT, 32 days and 8k miles), it all depends on what your plans are. I used hard bags for Alaska and they stay on the bike every day before and after. I am comfortable lane splitting on the Super Ten with my hard bags. The more aggressive you are in traffic, the narrower you will want your bike. And remember, soft bags still need some framework to keep they out of the tire and off the exhaust. There are rear bars like
Rumbux that give protection and soft bag tie down areas, or almost any of the hard bag frames that will give some protection and work with most soft bags too as tie down points.
Your needs are going to drive the direction your modifications, (we call them farkles), will go. I'm a big guy, I immediately found I needed my mirrors a bit farther out so I had a view of more than my shoulders. You can spend $30 on mirror extenders, or $10 for the same thing from
Lucky Bike . That was my first change in 2011 when I got my 2012 Super Ten and started riding it.
Ride the bike. See what you need or what you need to change to fit your situation. Shop around, there are tons of vendors and usually many different options for any one need. There is no perfect choice, only the choice that's perfect for you.