There is not much co-relation between accelerator throttle position and gear changing, but for better life of clutch plate, following rule for accelerator operation should be followed while changing gear, it will increase the life of engine as well as the life of clutch plate.
If you release clutch slowly all the time, it will decrease the life of clutch plate, because wear of clutch plate will be more particularity in higher gear position. If you release clutch fast, it will give shock on engine and gear mechanism.
To best practice is, when you change gear from Neutral to 1st position, release clutch plate slowly and put accelerator on high throttle, because engine speed is at low rpm in this situation, further lowering of speed because of engagement can stall the engine. There will not be much wear on clutch plate because rpm of engine is low.
Whenever gear is to be shifted up further i.e from 1st to 2nd, 2nd to 3rd, 3rd to 4th or 4th to 5th, release the accelerator to some extent, because at the moment when you shift gear up, momentarily car/bike will work on engine to make its speed slow, to facilitate slowing of engine at the time of changing gear, throttle paddle should be withdrawn.
Whenever gear is changing to lower position i.e. from 5th to 4th, 4th to 3rd, 3rd to 2nd and from 2nd to 1st, engine speed need to increase, to facilitate fast increase in engine speed, accelerator should be kept pressed. Best practice is, you should not release accelerator paddle at the moment of downshifting of gear.