I used the ring slings for all the things you listed just fine. I can carry LO in it MANY different ways. I snuggled him in a cradle postion when he was newborn, used kangaroo and budda carries, used it to just support his butt in a half lying position when it was hot (so his feet and arms could hang out to cool), and now use it to hold him in a chest to chest position with his legs around my waist. Oh, and I used it to nurse him in public many times -- no problems!
I also used ring slings outdoors loads. I was visiting a big city once for a week when he was 8 weeks old. I carried him all over in it for shopping and sight seeing. I still use it in the house when he needs rocked to sleep while I am standing (his favorite way to fall asleep) as I can stand there for ages and it is so much easier with his weight in a sling!
Now that he is so heavy and I want to put him on my back I have a mei tai that I made. I made it a little bigger than most, so he hasn't quite grown into it yet, so still likes the ring slings best. He still wants to be treated like a 5 month old even though he is the size of a one year old!
I was out Christmas shopping the other day (all day) and carried him in the mai tei on both my back and front. I was so glad for it! The shops were so busy and crowded and I saw LOADS of moms fighting with prams and bumping into things and not being able to get them around things.
I just walked through places with LO snuggly attached to me!
I find the mai tei less practical for nursing. The ring sling works better for me. But lots of ladies nurse in the mai tei with no problems.