I know this is my 3rd post but i have a lot of dnd builds but my question is does planar warrior affect sneak attack and sharpshooter. I was thinking assassin rouge horizon walker ranger 3 in ranger and the rest in rouge. Also does planar warrior alert creatures when u use it.

It specifically says "all damage dealt by the attack becomes force damage" - so yes - it would affect sneak attack and sharpshooter.

If you attack someone you reveal yourself if you're hidden (unless you miss and have the Skulker feat). There's no indication it makes any more noise than a normal attack does so it would be just as alerting as a normal attack.