How much Fps would I get in Minecraft multiplayer with this build?

That build is complete overkill for Minecraft. Your FPS would probably be around the 300s constantly, but remember that a multiplayer game is limited by your internet connection speed. As the best monitors on Earth run around 144Hz, you are paying more for power you won't notice or use.

60-300 fps depending on the amount of mods and your monitor's refresh rate.