Thanks for the help. I finally found a site that lists the info I needed in a comprehensible way without tons of errors.
In case anyone else has this problem, here is what I learned: once you pay the fee, you can travel.
1. Many sites conflate the passport visa with the IR-1 and the green card. Different things. It looks like the passport visa and the IR-1 are distinct, or maybe it's more correct to say the one they put in the passport is extended when the green card is issued. Not sure. The passport visa is just to get the applicant into the US, and ours lasts about 120 days. An IR-1 or CR-1 visa is what you get with your green card. The IR-1 visa lasts 10 years. A CR-1 lasts two years, because "CR" means "Conditional Resident." "IR" means "Immediate Relative."
2. A green card is proof you have the right to enter the US and live and work here. A spouse with a green card can get a bank account, SS number, and driver's license, and of course, it permits employment. A green card recipient with an IR-1 can apply for naturalization in 3 years.
3. The immigrant fee goes to pay for the green card, and it has to be paid before the applicant travels to the US, so the passport visa is not sufficient. You do not need to possess the physical green card in order to enter the US. After you pay, the green card automatically goes to your US address. The fee can be paid with a credit card at the USCIS site.
If I find out I've been handed any more misinformation, I will update the thread accordingly.