You should really consolidate all your questions into one thread and call it something like
"New guy with a lot of questions!" I actually have a setback Elita One seat post and it's very stable. In fact the seat post is very snug compared to other round seat post I've used. It was so tight I thought it was defective at first. I think it's meant to be that way to reduce over torquing on the seat post clamp. Just make sure to use lots of carbon paste. I've had no problems installing and removing it with CF paste. The saddle clamps do not need much torque to keep the saddle in place, so I'd just torque enough so there's no movement. I'm using a RYET oval rail carbon saddle.
Also I've seen replacement saddle clamp bits being sold, so if you plan on purchasing the seat post, you can also get the spare parts at the same time.