There is no high in the beta, the settings are all capped at medium (which is why it's only 1.5 gigs). If you're using play now, don't, it's stupid, it'll connect you to a european server or something with a terrible ping. Use the server browser and join anything under 100 pings, the servers are smoothed out now and assuming you're on a server that you get a good ping to there shouldn't be any server lag. That said, though, for the first 30-60 seconds after you join a game it tends to lag a bit, but that may just be buffering, I'm not sure what it's about. After that initial lag it should smooth out though.
Also, I went into settings.ini and changed my DX from auto to 9 and got a big improvement on performance.