I dont run tubes ever. On my own personal bike I put a hole into a tire during a long race, put my tube in it and flatted the tube with in a couple miles at 30 psi.
last weekend I demoed a anthem X 29er and the tubes tires on were a pain in the ass. Giant had them inflated to 38 psi which rode like
****. It was rough, had no grip, and rolled so slow because it was boucing off everything. I lowered the pressure to 28 psi. It rode better in a straightline but the tire rolled off the rim, and I pinched flatted the rear tire in rock garden at high speeds.
For me I simply can not ride the way I want to on tubed tire. I either have to run a high pressure and suffer though lack of performance, or run a low pressure and for sure flat it.
There is nothing better about a tubed tire.
bars and stem are personal thing. It has nothing to do with what size your wheels are. it does have to do with your trails, what your use to, what your willing to get use to, your bike size elect elect. I personal hate being in a really long position. I use a 70 mm stem with a very swept back flat 740mm bar. I also use ergon's and bar ends.
Improving handling? what do you need improved?
extending reach? why do you want your reach extended?
a slightly wider bar let you leverage in turns and tech areas better, also on Single speed it let me leverage on climbs better. You have to use a shorter stem though because your reach effectively gets longer as your bars get wider.
the bar ends let me get far forward while climbing while still letting me run my short stem, they are also quite handy on 40-50 + miles rides to keep my hands from getting fatigue on road sections.
the shorter stem lets me loft the front end alot easier and make it easier to ride trails aggressively. Alot of XC guys are now shorting their stems quite a bit even on the World Cup, but I think long stems anything 100mm and over are passe' and actually hold people back when riding singletrack.
again using what I use on my bike might not work for you. It could work for you and feel pretty awkward at first. You could extend your width a little bit and that should improve your handling and your lenghten your reach. you would be hard press to see a narrow long set up at any XC race these days. People just didnt know any better back in the day, and the kids these days like comfort and performance.