no, there's nothing wrong for ask something =)
depends. HD looks good if you have a mid-end or mid-to-high spec PC. DHD is better if you have a PC with beast spec and have triple screens/high resolutions monitor. but DHD will eat many of your FPS. as it takes more VRAM. generally speaking, HD is balance for performance and quality, and DHD is for better quality. choose one which suitable for you.
depends. HD looks good if you have a mid-end or mid-to-high spec PC. DHD is better if you have a PC with beast spec and have triple screens/high resolutions monitor. but DHD will eat many of your FPS. as it takes more VRAM. generally speaking, HD is balance for performance and quality, and DHD is for better quality. choose one which suitable for you.