No matter how good a person's connection may be, at the end of the day, FAF is FAF...
It uses a peer-to-peer connection and that will always be inferior, 'lag'-wise, to a server-based connection.
On another note, speedy connections are not always stable.
I once had a really fast connection, yet it was quite unstable, and though I could download any game within minutes,
my packet loss at times was high.
This resulted in my ping showing as really low, however, I would always be the source of 'lag' in large team games.
And since FAF uses Peer-to-Peer connections; a great factor in connectivity, here, is Geology.
The farther the distance from players, the more 'lag' you may encounter.
I don't currently have the best connection, myself, but, I tend to experience more 'lag' with players across the globe from my location than with players residing in the same continent / nation.
And, based on my experience, some 'lag' is just based on network activity.
For example, my matches at 9 PM are usually smoother than my games at 1 PM due to less network activity - again, regardless of network speeds.
Last thing, the more players... the more connections... the more 'lag'.
For every player that is in a match, the number of connections grow exponentially.
If you're in a match with 4 total players, at most, every player has 3 connections. That's 12 (ish) connections.
But, in a match with 5 players, every player has 4 connections. That's 20 (ish) connections
And FAF can hold up to 16 players in a match. That's about 15 connections PER player.
(Now, I'm not sure if this is precise, but, the overall point about exponentially growing connections, is made.)
That being said, here are some options for you to try out:
Try the "Force Relay Connection" option in the Client settings, "Forged Alliance Forever" tab.
This setting will most likely increase your ping, but it may end up being less jittery, overall.
The next option, "Allow the ICE Adapter to use IPv6" could also cause issues if you (don't) use IPv6, depending on your network settings.
Hope this helps!
~Stryker