Yes, you need at least 2, but 3 is even better. You need a small one in inch/lbs for the little fasteners. You want it to top out between 150 and 250 inch/lbs. That way, at about 70 to 80 inch/lbs for an M6 fastener, you'll be running in the middle of the range. I find I use this one the most. Next, you'll need a "midrange" one, spanning from about 10 to around 75 ft/lbs. You'll use this for most of the other fasteners on the bike. Then finally, you'll need a big one that goes up to like 150 ft/lbs. This won't get used much but is needed for things like axle nuts and the countershaft sprocket nut.
Some things I use a torque wrench on religiously (M6 case screws, caliper and disc mounts), others not so much (axle nuts, oil drain plugs, spark plugs). I found the single torque value given in my '78 shop manual for the axles rather silly. How can you expect the cotter pin holes to align when you reach that value? Right, you can't. So, I always just made them very tight. Eventually, I did discover a better torque chart, one that gave all the values in ranges. It's the one from the '77 supplemental manual, and the one I use for most everything now .....
Using this, I have now checked my axle nuts and found I have been meeting at least the minimum given spec.