To be able to play games at good performance, I need to plug in my charger otherwise games will drop down to unplayable frame rates. But most of the time, my laptop is already at 90-100% on battery life, so I'm wondering if this will destroy the battery over time if the charger is plugged in too much..
Correct it is not good for the life of the battery. My old Sony laptop which I used to game on had a battery care option and this recommend either 60% or 80% maximum charge state if the laptop was constantly plugged in and would stop it charging once either 60 or 80% was reached, the laptop became too old so I moved on but the battery was still good after several years. I no longer game on a laptop since getting back into desktop gaming and don't really worry about my work laptop.