Sounds like you have a rock solid plan here! The following is what seems to work best for me.
Thicker steaks tend to work better when doing a reverse sear. 3/4" and up with about an 1" to 1 1/4" being the sweet spot.
Bone in makes all the difference.
My three favorite seasoning (in no particular order): kosher sea salt & fresh cracked black pepper, Montreal Steak Seasoning, & Uncle Chris' Steak Seasoning. Regardless of what you season with, finishing with good flake salt seems to just knock it out of the park. I'm on the fence about finishing with oil or butter. Makes an awesome display, but just haven't found the one that knocks it out of the park for me in terms of flavor. So still experimenting here.
Sometimes, I go straight up meat and do nothing after the salt and pepper. Other times I'm doing sauted mushrooms or a cutting board sauce.
I've found that I get mixed results when using cast iron to get a hard sear in the Traeger. If I'm going to use cast iron or want a hard sear, I tend to fire up the Weber grill and heat up the skillet that way or even just go straight into the coals. Alternatively, the sear I get with just using the Traeger (no cast iron) is often just fine.
While timing, touch, look, and experience all are okay for judging when a steak is done - it really is all about the temp. Internal temp specifically. The best and most consistent results I've gotten have been when I have smoked the steaks at 180-225 (lower temp tends to mean more smoky flavor) until the internal temp is 120. I have been known to pull as low as 118 if I have a lot going on and don't want to take the chance of over cooking. Key is not to go over 120.
Either taking the Traeger to as hot as it will get (400 to 450) or using an alternate sear option the most important thing is making sure I don't blow past 125 internal temp is making sure to let the steaks sit for 3-5 min before searing. That short rest lets the steaks equalize a bit before putting that final sear on them.
Before carving/serving its really import to let the meat rest. Resting the steaks under loose foil for 3-10 mins (longer times for thicker steaks) not only lets the juices redistribute, but you also get carry over cooking of 3-8 degrees.
This is what works for me and has been the result of a lot of fun experimentation, hope there are a few tidbits that you find useful.
Steak on!