Hi there,  My son is making us collect the Thomas trains in OO scale.  we have a bunch of the other brand (Hornby).  He has asked me specifically "Bachman Percy" 

is all Bachman Thomas in HO?  Is HO and OO out noticeably?  Please weigh in with opinions please.

this is the one he wants.

https://www.worthpoint.com/worthopedia/bachmann-ho-scale-thomas-friends-1807241375