I support your decision to go to a fixed head over a mechanical. I know guys use mechanical and they work when they work most of the time but I have also seen them fail on whitetails with a less than perfect hit, but one where a fixed would have passed through or nearly passed through. So off to a good start. I am also intrigued by the narrow but heavy arrows such as the Easton FMJ although I have only used regular diameter Gold Tip Hunters. Take a cue from the traditional guys and read a bit about penetration and consistency with heavier shafts and heads. Don't go crazy heavy, at the cost of trajectory at 40 yards, but stout would be good. A solid fixed head such as a Montec or Woodsman will get the job done with no drama. No replaceable blades to fail. Make sure you have adequate FOC, no 80 grain heads with your long draw. I would also get away from the mini-fletched arrows and go for a full size fletch / vane. There is too much riding on your shot to miss due to a funky broadhead flight, and there's no guarantee your form will be perfect from the ground setup you might have or after running up a steep slope at 10K altitude or in bad wind. Try to account for less than perfect, even slight mistakes, and go for a forgiving setup, you don't need to drill 1 inch groups on an elk, but you sure as hell don't want to miss, and it happens much more often than you would think, and I say that with personal knowledge. So don't be like me - and learn to judge range accurately on an elk, they mess up your internal rangefinder if you are only used to deer. And so does the terrain, steep angles, open country maybe, etc.
I am sure there is much more to consider but your willingness to modify your usual thinking from PA treestand to go after a totally different game is a good indication you will be all right.