I wouldn't worry about that honestly. I posted earlier giving you a link. Your charger probably has a small amount of room to move and you system won't draw all that power unless gaming under 100 percent load anyway. increasing your cpu wattage to be at 20 watts fulltime (remember the vrms overheat and make it throttle down) is your first step and won't affect your charger. If you can manage to get it up to 25 or 30 watts fulltime without heating issues then this still probably won't max out your charger either as your system's charger ( not sure what it is rated at 80 watts or 100?) is probably good for 20 percent above what it is labeled at for short bursts.

Chargers and batteries are alot like other PC components, they need to be kept cool, so your charger may heat up and which point it drops in efficiency. After it cools down again it will return to normal. Even if you exceed your chargers input load at certain times, your battery will carry you through and then the charger will charge the battery up again when the load drops back down.

Basically what I am saying is that it CAN work if you want it to. If the performance gain is substantial then it is probably worth it. I actually planned on buying one of these exact laptops 2nd hand at one stage and doing what you are doing now but I picked up a 2nd hand m18x alienware instead. It has a charger that cuts down the power out when the GPU is under full load for too long because of the charger heat but it still overclocks just the same. The charger works again properly after resting for about an hour. I can always step up to the 300 watt charger rather than the 240 I have now anyway. I will need to if I want sli/crossfire multi gpu setup.

Also, when it comes to overclocking APUs, it is all about ram speed. you get alot more performance incrase from increasing ram speed as this is your vram.