Huh, looks like with my Chinese copy of Intel 8260 AC (TL-8260D2W) — the iwlwifi is the good choice since the great work made by #FreeBSDFoundation Laptop Initiative
(if I don't care about upload speed. And yes, I don't care)
Iwm driver: 10.1 Mbps / 2.6 Mbps download/upload, 29 ms jitter (1st screenshot)
Iwlwifi: 22.4 Mbps / 5.0 Mbps download/upload 0 ms jitter (2nd screenshot)
Wifibox: 17.4 Mbps / 27.8 Mbps download/upload, 0 ms jitter (3rd screenshot)
Obviously the same (shitty) AP from ISP was used.