I've made macarons for years. I have never had any luck with the Italian Meringue version. I really don't like the texture of them, I find them the shell too hard and too sweet for my taste.
I worked for a caterer where I had to make 2500 over three days (5000 shells). I've always used the French Meringue version and will have an occasional flub, but they are just temperamental and it's because I will over fold when I haven't made them for a while. Once I'm back into it, they are fine. I've worked on the recipe for a while, adding a little dried egg white for stability and tweaking here and there.
I've seen many discussions on this subject, but you just have to find which one works best for you. I've read that the Italian method can be easier for making different flavors and colors from one batch, but wouldn't know personally.
Once macarons are made and sandwiched, they freeze very well. Just let thaw in the fridge and they are fine. You can freeze the shells as well, you just have to store them well to prevent breakage.
The cookies need to rest 24-48 hours after sandwiching to get the right texture. The shell will absorb the moisture from the filling to soften it.