so for example an assault vest on watchdog increases its stats if I used baton pass will it pass these on to the next Pokemon or not ? thank you for the help :)
No, that would not be passed on. For two reasons:
Baton Pass only passes down changed stats. Like if my scolipede used swords dance, then baton pass, your next Pokemon will have the swords dance boost. If you want to switch items then try the moves trick and switcheroo. Hope this helps!