Off-set and tires for an 02' base Boxster

[HotwheelsUSA]

I have a 2002 Porsche Boxster base that I am fixing up for my son. I just ordered wheels for it and the seller assured me they would fit my car and not need any spacers. They came in yesterday and the rears will for sure need spacers. The company I ordered them from is being nice and offering to pay for some spacers but the kind they want to order does not seem safe to me. They are just a spacer with longer lug-nuts. When I built my 72' 911 Carrera a while back (12 years ago) these kind of spacers were not recommended. I also dont trust that they know the correct size of spacer to use. They are telling me a 20mm (a little more than 3/4") and I saw the same wheels on a car on line that used 1". The wheels offset and size are:

Size Staggered : Front 19X8.5 Rear 19X11
Offset : Front +53 Rear +62

Does anyone know what the best spacer size would be and if the bolt on spacers are better or safer than the kind listed above?

I also would like to know the best tire sizes to get as well...Before the tire shop orders some in that I wont be happy with.

Thanks in advance to any help or advice!!!