What do you mean by "cant make a straight line"?
If you mean the line you draw is curved, that's because these mice don't have angle snapping.
If you mean the line is running diagonal, like "from top left to bottom right" or "from bottom left to top right", that's because of your grip.
Get higher speed memory and manage to run your game at 240+FPS with all kinds of v-sync and buffering turned off before you talk about mouse precision.
Memory speed and efficiency is the KEY factor to improve framerates in ALL multiplayer games (eg. OW, WOW, CSGO, LOL, HOTS). CPU frequency or GPU power is NOT.