Valid questions. The stock sprockets on the TW200 are 14/50 or 14/45, depending on market. The TW200, properly jetted, will run 75mph at redline, with 14/50 sprockets. Unfortunately, the TW200 is so lioghtly stressed the engine will not pull 75mph under most conditions. Fortunately, the TW200 engine, properly jetted, is so lightly stressed, it will run WFO at 9500rpm tank-to-tank. It sounds like it's screaming its guts out, but it isn't. TT-R 230 engines, same engine family, are still dependable at 28hp output. The TW's 12-13 horsepower is nothing to the engine structure. Let her spin. Considering these facts, go ahead and add a dual sprocket set-up, the instructions are on this forum.
The Motoman break-in is inappropriate for the TW's 1960s engine technology. The Motoman break-in is appropriate for engines with contemporary engine technology, with liquid cooling to provide a more stable control of thermal expansion and contraction and coated cylinder bores to reduce friction, which permits much closer engine tolerances, and much smoother machined surfaces, such as a CBR or such. The best break-in for engines with the TW's level of technology is a couple dozen miles of easy riding, change the oil, then lots of short, steep hills in a relatively high gear that requires high throttle application at moderate rpm going up, then low throttle application at moderate rpm going down. Constantly changing engine load prevents and cold and hot spots from developing in the combustion chamber walls (piston crown, cylinder walls, valve heads, and cylinder head). Cold and hot spots can affect the temper of the metals involved and detract from engine life. Since you can't undo what you've already done, I suggest a nice, patient ride on a curvy road or trail through hilly terrain for the next 500 miles or so. after that, run it any way you want, as long as the jetting is good. You'll notice steadily increasing power output until about 2000 miles.
The Clarke XT350 tank isn't a bolt-on, but installation is not exceedingly difficult. It holds a full 4 gallons of gas. You'll need 2-inch handlebar risers to clear the tank, which most riders find more comfortable than the stock height.