Based on whether your planning to play pixelmon or pixel spark and i'd need to know more specification about your computer but generally but for me to play pixelspark which is pixelmon along with several other mods i only use 2gb of my 8gb or ram and i know its more intensive on the cpu side my processes is only an AMD a8-5545M which give me about 1.7 GHz which is rather small but the game still runs at a smooth 30-60 fps for me so I'm sure your computer will run fine despite most Pokemon looking hd the are actually rather low poly and just higher on the texture and and entity number end so if you just make a few graphical changes such as render distance in your settings I'm sure you'll be fine give it a shot.