have some answers for you and hope other would fill in
1. Most of the dvr cards are offered in window based since window os is the most common. I know of linux based card from original supplier but i do not know if i am permitted to give out their names. Some offer them with DOM while others just image.
2. Yes, the quality of the your card is directly related to the quality of your recording.
3. Yes, generally speaking, you can attain almost realtime display on LAN, but personally i have never seen a realtime display on the internet yet. Maybe realtime display for one channel/ two channel but never for a 16 channel. Again, personally i mean. Bandwidth limitation.
4. Most of the dvr card including GV, would recommend Intel chipset motherboard.
5. I would also like to see a list of the most common dvr card available. Hope someone would post a list very soon. Anyone?
6. You could start by looking for those paid advertisement in this site. Not the one by google ads.
7. Yes, all legitimate dvr card should be package with their original software.
8. In my opinion, if you purchased an orginal dvr card, why settle for a generic software? Those who settle for generic software usually are those who have pirated cards or original card which already lost it's identity.