I've never adopted one from a shelter without research.
But I've adopted strays, without.
Even when you do research, you can still sometimes find things out about your particular animal, afterwards. For example, if it is a mutt, you might discover a breed they have in them, that might have some health or behavioral issues you didn't know about. So you have to be willing to bend, but then nothing about life/animals is cut and dry. Animals have taught me so much!!