When I camp/hiked Sipsey, we parked at the Thompson Trailhead. It's the NW entry. Hiked south to the Shiprock/Eye of the Needle area. Slung hammocks just past Shiprock on the river, then hiked up Bee Branch to see the Big Tree. From my study of the top map and from what I saw, the place is not that difficult. Not much elevation change because the whole thing is basically a cracked up, eroded slab of limestone. I think the highest cliffs we saw were only, maybe 200' feet higher than the creek/river banks most of the trail is on. Most less than that. You could get jacked up there, like falling in the river or whatever, but it's not that bad.
Be aware that the trails are obvious, from the traffic they see, but there are no blazes and I think we only saw one sign the whole time. Bee Branch sections had a lot of blown down timber. Some of that timber is amazingly large, too. That got rough with the packs, climbing over and under them. We actually ditched them hiking up to go check out the Big Tree.
It is an unusual place. I've not seen anything exactly like it in our state. It is rather primordial looking. I was told that the place was never timbered, ever. I find that easy to believe. I would advise carrying a topo map of the place or a GPS with topo software. An outfit in Birmingham makes a nice map of the Sipsey. "???????" Cartography, I forgot the name. I've seen their maps for sale at both Alabama Outdoors locations or you can get them at the cartography shop itself.