I recently finished a 60" tip to tip, 45# at 28", One-seed Juniper that I backed with rawhide. I made it from a 3" diameter branch or trunk from the tree. One-seed is a little different in that it seems to have multiple trunks, or a main trunk and other occasional vertical branches. I'm not sure which.
It's a visually beautiful wood. The bow ended up with a belly of mostly heartwood but edges of white sapwood along both edges. One limb had some unhelpful movement in the grain so my decrowning wasn't perfect, but I'm not seeing or hearing any issues with it. Between the rawhide and the relatively light weight it's doing very well, and is a pleasure to shoot.
Which type of juniper are going to use? The juniper I've seen in southern Arizona, mostly one-seed and Alligator, can be a challenge to find an appreciable length without twist or knots, mostly knots. I suggest that if you can find a good branch to meet your needs use it first. See what it does, see how you do. Cutting a limb won't kill the tree but cutting the trunk would. A lot of junipers are hundreds of years old. If you can find a straight one that'll give you 68" staves guard it carefully and be sure before you cut it.
And, just to be safe back it with rawhide at least.
My wife is a big fan of bow building now thanks in some part to the smell of juniper in my shop while I was working on this bow.