The "SET Lua memory..." thing is to stop the UI error popups.
For FPS problems (and the problem is not your computer, but the game that isn't very well optimized yet), read this post on reddit: Are you having FPS issues wih ESO on a PC? Well here's an in depth Fix along with performance upgrades + tweaks to Graphics.
I read and I only made changes that I thought necessary, always giving preference to maintain the most quality possible. I got an improvement in performance, but in PvP (with a lot of ppl around) there is no solution: I have to disable almost all addons.
I really hope that with the next DLC, the 64b client will be a lot more stable, giving us a lot less headache.