48L panniers should be OK,
But bring a large (c 50L) waterproof stuff sack
I always put the sleeping bag, in a waterproof stuff sack, (There is only one item that can never, ever, get wet, your sleeping bag!)
The sleeping bag, in its own waterproof stuff sack, goes inside the large stuff sack with the tent (also in a stuff sack) and the stove (in a stuff sack) and maybe some food on the rack in between the panniers.
The tent poles, are attached to the underside of the cross bar, in a specially made tent pole back with big velcro straps.
All important stuff (documents, money, camera, glasses, phone) live in the front bar bag
The panniers contain clothing, food, wash kit, and that is all.
You need the same amount of kit for 3 days on the bike as you do for 3 months.
Do not over pack, you can always buy extra items if you need them, once you are on the road.