Andy, Spiky growth, similar to that of a needle juniper, is what we you would see as juvenile foliage. Itoigawa is a mounding juniper. So, what you will typically see is that an itoigawa will mound, create an almost bushy nature of growth on a branch, and then, from that bushy growth, you will get these extending shoots. Those are the majority of what you have pictured here.
What to do with them: It depends on what you want. Do you want the branches to extend? or, do you want the branch at the length it currently is at? If you want them to extend, you definitively want to leave it until it gets to the length you want. Cut it above the lateral shoot you want to start building your secondary and tertiary branching at. If you want it at it's current size, cut the long shoots back to slightly before the current pad you have. It's all about what you want. But those shoots suggest vigor, strength. The tree is ready to extend.
However, keep this in mind. Any tree that's ready to grow will want to grow long and tall, so, it'll put it's energy into those long shoots. When it does, less resources will be given to the current growth you have. It'll start to drop the pieces of growth closest to the trunk and moving up as those shoots grow up and gain mass. The tree says, these tall shoots are the strong ones that get me out to the sun, I don't need this interior stuff. So, if you want to grow it out, understand you will see some of that stuff close to the trunk die off. When it does, it's not a problem, just the growth pattern as they start to be shaded.
Juvenile growth: You made one mistake in your handling this spring. You repotted and cut off branches at one go. When you repot, the tree needs the photosynthesis from it's foliage to repair it's roots by feeding them with carbohydrates and sugars. The tree pushed that juvenile foliage as a result of that. Do major branch pruning in the fall, do your repotting work in the spring. not at once. No biggie, the tree is strong. We learn from these mistakes.
