1) That is a fine configuration. It would be good to know the maximum capacity of the computer for RAM, even if you don't configure it that way initially. RAM is very easy to upgrade later once you find your models no longer run in memory (in-core).

2) Those who choose gamer cards instead of cards from the Tested list run a significant risk of a problem with ANSYS software. I expect that you will have a very small risk of a problem choosing a Graphics Card Tested that supported Windows 7 and have a good outcome with Windows 10. The risk is smaller when you choose one that was tested on Windows 10, but you have a budget to respect.