Generally, Jim recommends keeping the supplemental lift the same as the main lift.
As far as the second question, it all depends on your situation. I feel that I can give some input on this because I've done it.
At the start of my lifting, I tried out a lot of those LP programs like Starting Strength, Stronglifts, Madcow, Greyskull LP, etc. They all work the same way. I feel that Starting Strength is really great for introducing new lifters to the barbell. After they do that for a little while, 5/3/1 is where it's at. A lot of people label it as an advanced program, but that's nonsense. Don't let yourself get into thinking that other programs work better or faster. It works, and works well. There's nothing magical about this program or any program. You just can't be stupid about how you use it.
My advice (If you want to take it from someone that's not Jim)
Learn from this forum. Spend some time looking around at the questions that have been asked. You'll find a TON of information on here.
Learn from Jim. Really try to learn how he views training, how he views life. His principles have created an evolving program that is EXTREMELY well rounded. It's focus is on athletic performance, and just kicking ass. You will be tempted to change what he suggests, but you shouldn't do it. Open up your mind and trust the man. So many people, myself included, have done this and it never works out. Trust the principles of the program.
If BBB speaks to you, try it out as Jim suggests it for a few cycles or run the challenge once through. I wouldn't recommend sticking to it forever.
Lift, Run, Stretch, Eat.