I think the AAP recommends keeping them in your room til 6 months to help reduce risk for SIDS.
On that point though, esp now that we're on our 2nd, here's my takeaway to 6793026:
Take care of yourselves! There's an infinitely long list of things that are "best" for your kid. Stuff like SIDS prevention, breastfeeding / pumping, how / when they sleep, what kind of music you even have playing, how / how much you talk to them and sing to them.
But if you guys push so far on some of this stuff that you're on the brink, it's actually so much worse for the kid and the family overall. So just do what you can, and try to stay positive for each other and the kid.
Also, "every baby is different" will be a handy phrase to keep in mind, and also to say to parents / in-laws / anybody else being pushy with you. It really is true. We just had our 2nd boy and with only 18 months apart, I can compare them back to back, and I can definitely say they are very different in needs and behavior. Take all wisdom with a grain of salt, and feel free to determine what works best for your kid and your situation.
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In terms of gear: look into getting a baby carrier!! I have a Lillebaby and my wife has a Bobawrap. It'll save your sanity because when the baby is screaming and screaming, and you've done everything you can (they're fed, diaper's changed, temperature OK, etc) and really they're just grouchy for no reason - which will happen all the damn time - holding them to you and bouncing them is the only thing you can do. And that gets tiring after a while, as well as ties up both arms so you can't do anything else. With the baby carrier, you keep them happy while you're freed up to go do other things. Like post on RS!!!
And on car seat - stroller compatibility: I put a huge amount of priority on our infant car seat being able to latch directly to our stroller w/o adapters, and it just really wasn't necessary in the end. You're not even supposed to leave a baby in a car seat for more than an hour continuously, they're not that comfortable, and car seats aren't really that heavy to carry by hand: so often we didn't even bother for e.g. visits to the pediatrician.