Just my opinion, for what it's worth. Having played with the 180's quite a lot. I would stick with the 168's in the Rem Mag. The case capacities are right on that knife edge of being able to take advantage of the 180. Not quite enough to make it sing. Short neck and a short throat push the 180's deep in the case creating enough lower velocity to not quite make it worth while. Depending on your accuracy node you may be as low as the low 2600's FPS in a 24" barrel unless you really hot rod the brass....and seriously, who wants to be doing brass prep all the time? H1000 is absolutely the right powder, and the reports in this thread of velocity around 2950-3050 with 26" barrels are probably very legit with max loads. H1000 will produce a screamer load if you are patient and work in .1 gr increments. Super stable across temperatures.
In the 7mmRem Mag, I think you are better off with the higher velocity 168 class and the less robust bc.
You give up 12gr bullet weight, and what appears to be serious bc, but you gain at least 200fps....... you will absolutely notice the wind call difference with that TOF delta. If I'm going to shoot a magnum, I want magnum velocity.
There are of course custom rigs, but at that point, you should seriously consider something with more case capacity. I personally would step up to the Weatherby case with the 180. All the rest of the build stays the same. Source the brass from Norma and the dies from Forester. 7% more case capacity and you can still run around 3000 in a 24" without a compressed load.
The 180 is an absolute hammer. Drops them like a sack of hot turds.