Does charger affect performance?

Depending on the system, it can make quite a large difference. Have you noticed a difference in performance between playing on battery and playing while plugged in? If you run some monitored benchmarks, you'll find that unless you set your power profile to performance (and accept the loss of battery endurance), you'll lose a large chunk of your gaming capacity. Even set on performance you'll drop a measurable amount. A laptop battery just can't match the power coming from the wall.

Running your laptop with wattage lower than your system is rated for has the same result, although maybe not to the same degree. Your laptop will pull what it needs from the adapter - if you have a 65W adapter and your system is only drawing half of that for operation, it will divert the other half to charging the battery. If it needs the full 90W, it's going to pull 65W and distribute it accordingly, so all of your components are going to receive a portion that's 28% lower than optimal. (It's not exactly proportional, but that's close enough.) Some laptops make up the difference by drawing on the battery, even while plugged in. Two of my laptops have 120W adapters (20V/6A) - I have a light travel charger that pushes 75W that I'll use when I don't want to carry the brick. If I try to game using the travel charger, my laptop battery will drain itself even while plugged into the wall.

A good rule of thumb to use with laptop power supplies/adapters is to keep them +/- 5% of the required capacity. Any more and you risk frying your system; any less and you'll starve it of power.

Make sure that the new charger supplies enough current (shown in "Amps" (it's fine if the new charger supplies more)) and the voltage is the same. If so then you will be perfectly fine. Although this may work, some laptops might have some adaptive charging technology which means you might notice a little change in charge time but nothing severe should occur.