i am unsure of the clear coat application thickness on a new lexus...
where is the scratch? typically, you will have more clear on horizontal surfaces vs. vertical.
i'd get a PC or Flex as you mentioned, run a 4" orange pad with some menzerna super intensive polish or optimum polish and see if you can't get it looking significantly better.
i know for a fact that a 4" yellow spot buff and a PC and optimum compound will take that scratch out, if not almost completely, but you would then have to refine the area after that with optimum polish or some sort of equivelent product. i feel it's best to start out with the least aggressive mode and take a little more time with that to assure you don't remove too much material. i'd try a PC or Flex because you'd be removing clear in such small increments (in terms of wide area as well as depth) vs. something more drastic like a rotary, ESPECIALLY if the rotary is using a small pad too. very easy to do some damage there...
again, though, without a gauge and/or personal experience, i have no idea how much clear you have to play with.
good luck!