Id do a pergola with clean lines with retractable blinds/shade in the roof part. There are some DIY blinds on Pintrest. For your windows I think external blinds that stop the heat hitting the glass are your best option.

Listen to your architect. Grey/silver looks clean and will never date. We took our architects advice and went with silver. I like the fact that they blend into the scenery and house and are not a feature you see. I do not even think we had aluminium frames mid 20th century. Wood?? Black frames I believe became popular decades later.

The difference is amazing. Stone and water just WORK together, and the combination of brown, rust, cream and gold with the blue that picks up the colour of the pool is a match made in heaven. Great result.

any gas log fireplace should have very specific instructions for safe installation with measurements for distance from back and side walls, height above floor and height of any mantlepiece above the front of the heater and details of the correct method to enclose the flue..first check these instructions and then decorative finishes will be much easier to decide...if you haven't chosen your heater yet all the instructions should be available on line and this will also help decide the best heater for the space available