Great questions, Athena!
1. When I encounter spirits in the ether it is usually by sight, but I've also encountered them only by feel and sometimes only by sound. Haven't smelled one yet.
As for how they look, that depends entirely on the situation, location, and the nature of the contact. Often they appear as they did as humans, and sometimes they are just energy.
2. I didn't know if I could find her in the ether, but I wasn't going to let the opportunity pass me by.
However, had she reincarnated, I still think I would have connected with her higher self, the part of her that stays in the ether even when she is reincarnated.
During a reading I try to connect with the deceased relative of their choice, but those spirits aren't always available to me. It's like I'm ringing their phone but they may not answer. Usually, though, I connect with people who are recently deceased and still have some unfinished business with the living or when that deceased person is still hanging around to try to help ease the sorrow of their passing.
3. Why did he have a backpack... I'm not certain. He was dressed in hiking clothes. If I had to guess, I'd say he died while hiking and on his way to the afterlife he still appeared the way he did when he died. But I honestly don't know for sure.