3D designer needed

I need to optimise some models I have for use as 3D web and web AR models. Currently when I use what I have the polygon count is too high affecting load speeds. I have the original CAD files which can be saved out as different formats. Having used .stp and .igs imported directly and also processed .glb though keyshot the count is always high. The platform I have used to create the AR capability is Vectary which is simple to host from but any experience of other tools would be welcomed. Ultimately I want to be able to provide AR from a web page or QR code.