Steam - Windows LINUX - Online framedrops

[mr.burpalestick]

Hello everyone !
(New on the forums, I'm not sure if this topic is at the right place ... please do tell if it needs to be replaced elsewhere :) )

I always have huge framedops when playing online (unplayable), whereas the game flows just perfectly offline.
The drops are only on my end. Nothing unusual on my opponent's end (we usually have ~20 ms pings and green indicators).

First, I've checked an "old" topic with very similar descriptions of the problem :
http://skullheart.com/index.php?threads/pc-version-lag-that-wont-go-away-solved.499/

Althoug the -ggpopingfix command seemed to be implemented by default (isn't it ??), I'm still encountering the same symptoms on my end. I can't tell if it's my laptop being unable to follow online play ? Or could it be some specific Linux related thing ?

I'm wired (no wifi stuff, ever), on an optic fiber connexion.

Spoiler: Speed & Ping Test results

SPEEDTEST
Ping = 13ms
Download = 94.86 Mbps
Upload = 38.01 Mbps

PINGTEST
Line Quality : B*
Distance from server : 150 mi
PacketLoss = unable to test. No Java installed --> Linux thing ??
Ping = 43 ms
Jitter = 3 ms

Spoiler: PC specs

DELL Inspiron 15R N5110
CPU : i5 - 2450M @2.50GHz
GPU : Nvidia GeForce525M (+Intel HD chipset but it's actually disabled due to Optimus technology not supported --> forced to Nvidia Gpu)
RAM : 4Go

Spoiler: Operating System

Kernel : Linux 3.13.0-101- lowlatency (x86_64)
Distribution : Linux Ubuntu 14.04.5 LTS
Desktop environment : XFCE 4 (Ubuntu Studio)
GPU driver - 4.4.0 Nvidia 340.98

I've been searching for a recent similar topic, but didn't find anything...
I'd be greatful if someone has any hint about what it could be about. Do tell if some more info are needed, tests I should do on my end etc.

Thanks in advance for any help !