I'm 5' and found it was best to go to an outdoor shop (Tiso in my case) and a staff member there helped me with getting a suitable rucksack that fit properly (in my case it was the women's Osprey Renn 65). Being a bit taller you may find it easier/have more choice of packs than what I did, I think there were two that were suitable fitting-wise but one of those really didn't feel at all comfortable so I was left with a choice of one
While I haven't done and long-distance backpacking, I do have to keep the weight/bulk of my pack down even for short distances. I got a great deal on an end-of-range down sleeping bag at I think it was Go Outdoors. It is so compact, light and keeps me warm, though I do prefer to be cool when sleeping and of course have an additional doggy hot water bottle which means I can still end up getting too hot. The other side of that though meant there was space for me to take the dogs inflatable camping mat. Of course, having the dogs I have a slightly heavier 2-person tent rather than a one-person tent.
I think my pack - backpack, 2-person tent, sleeping bag, camping mat x 2 - comes to less than 6kg and it isn't the top of the range gear if that helps with the weight of those things.