Hello, to answer your 1st question, yes a white quartz countertop it is very reflective and possibly blinding when exposed to direct sunlight.

I would get out to a yard and have a look! A pure white granite with minimal specs? I can't say I have seen one! You may have to look into another material - you will also need to make sure you specify it is for outside - not all materials can go outside... I would also suggest looking into Dekton - it is a porcelain material that can be used everywhere and that comes in solid white...

I agree with WW about the gloss white being a bit blinding, but use umbrellas and even nice place mates or decorative runners to help cover that!

Good luck!

Quartz (of any color) does not work well outside. Dekton does.

Any of the sintered (Dekton, Neolith) or Geoluxe, absolutely no engineered stone or resinated natural stone.

DO NOT use man made quartz outside. The manufacturers will not warranty the product and most recommend not using their products outside. If you're looking for a white coloring your best bet would be quartzite, which will have some movement.