Hi tg1
Haven't used p1 personally but it's an ok water based polish from what I've heard and read, C3 smart Nuba won't last 5 mins on rims so go for fk1000p which will last ages, I use fk1000p for every job unless nano protection is requested,it's hardcore stuff and can handle the heat from the brakes,
C3 on the body will give great results if your prep is spot on and is very quick and easy to apply,
Z8 is fantastic but I'd only put it over a sealant as it gives a different finish compared to a carnauba based product.
So it's down to the finish your after really, C3 layered will give a nice warm Nuba glow,beading etc,Z8 will be more glassy and reflective.
Have used most of the G-techniq range and IMO its a great range and not overly expensive,great performance and finish.
Haven't really had a lot of experience with Zaino products as such,dabbled in the past but never really got into it but have now got pretty much all of the range and will be using it intensively over the next 6/12 months.