Question one.
Everyone sleeps differently and in different conditions so no one bag fits all. I have had a few down bags and they last a long time, so it might be worth it to spend a little more for much better quality. For me the Cosmo 20 down does not have enough fill power (hence more weight for less warmth IMHO). It also is heavy. Nowadays anyone concerned with weight seems to gravitate toward bags that weigh 2.2 lbs (one Kilo) or less. The sleeping bag is one of the "big three" where you can loose weight. I would also go for a Pretex or equivalent shell. It does not have one.

Question two.
I started with army surplus gear years ago and cheap clothing I got at good will. I'm now able to afford better and lighter gear, but I did just fine and climbed a lot of mountains in old wool army pants and cooking in my old boy scout mess kit. I still see young people carrying 40 to 50 pounds! I would say they are stupid except I did that too, years ago. When you are young weight is not as important. As you get older and wiser you start replacing the old heavy gear.