not exactly.
final speed is based on the RATIO of the two sprockets.
ie, 10/44, the standard combo is 1:4.4
10:55 i 1:5.5, etc.
less ratio...= faster top speed, less acceleration.
the reason you use the largest front sprocket possible is because the diameter of the sprocket is larger...liken it to a spanner on a nut... the longer the spanner...the easier it is to tighten the nut...less strain on the chain.
the chain also has to wrap around the sprocket. the larger diameter the sprocket, the less the chain has to "flex" from being straight, to being curved as it passes over the sprocket.
ie, using a tiny little 6tooth sprocket (like on those cheap 50cc pocket rockets) the chain is almost folded in half as it travels over the sprocket.
whereas with a big, 20 tooth sprocket...the chain is closer to straight.
the more the chain has to "wrap", the more friction, the more wear it receives, combine with more stress from the torque issue pointed out above, the faster the chain itself wears out.
of course, there is a limit to the sizes you can use whilst retaining the required reduction ratio AND keeping chain speed down... bigger sprockets travel further, and the chain, being heavy, tends to fling away from the sprocket.
theres also the crankcase/sprocket cover that limits just how big you can go.
its all a bit of a fiddle, therefore...just stick with the stock standard 10 tooth sprocket and play with the rear sprocket only.
hope that clears it up.