Yeah as @Mathosu said, you would at steady at one specific point. Horizontal Aim Assist should be fine for most people and I wouldnt risk using something as blatant as vertical on good PVP Servers as it is very obvious.
I use Vape Lite and this does not happen. If you have a semi-good computer (like me) then 30-40 fps loss shouldnt matter as it should be around 400-500 anyway. If its not then try and get the OptiFine mod (Download).