I sent a ticket, the support said overlay stuff might cause this. I tried without arcdps, dx912pxy, yolomouse and discord. It was worse (because I disabled dx12 addon) but the game actually used my nvidia gpu, or so I thought. I read that dx12 (not the addon, the actual directx12) has a feature that makes stuff use both integrated gpu (intel graphics) and normal gpu (nvidia). TLDR: That means there is no actual solution other than using dx912pxy, at least in my very specific case. If that addon didn't help, you should also send a ticket. I decided to enter in GW2 Development Community discord in which there is the "dx912pxy" section and they said me my setup is bad for playing gw2. Anyway they gave to me some advices that I'm trying to apply.Anyway the link is: https://discord.gg/avUzAzjP