Flying to Seattle is not a bad idea, especially if you do it in conjunction with a mountaineering class from one of the schools and/or guide services there. The Cascades are an ideal place to train for the higher ranges and you can learn a lot in a 6-12 day course.
Trangos (especially the Trango S Evo) are relatively soft, flexible and light for mountaineering boots so fit issues are going to be less obvious than in an absolutely rigid boot like the Inverno or Nepal. For the Inverno, experimenting with socks, insoles, and lacing strategies can help a lot. For hiking in plastic boots, the trick seems to be keeping the lacing loose enough to avoid shin bang and tight enough (in the right places) to avoid excessive heel lift. You can tighten them up more for technical climbing if needed. If that doesn't work, you could try swapping out the stock liner for a thermo-molded Intuition liner, which will be custom molded to your foot shape, and see if that helps; it will probably also make the boot lighter and warmer. For the Nepal, breaking in the leather a little may help. Also, as Grampahawk noted, you can adjust the fit of Nepals quite a bit by using the removable tongue insert, trying different socks, and using an insole. It took me several months of fiddling with the tongue inserts, trying different sock combinations, and different insoles, to get my Nepals to the point where they were comfortable.
B.t.w., do you have any specific mountaineering objectives in the near future? That can help you choose a boot. The three boots you mentioned (Trangos, Invernos, and Nepals) are designed with different types of climbing in mind. There is no one boot that's optimal for every type of climb, and you can expect to buy multiple boots for different purposes if you get into the sport. If Trangos fit you well, then they may be a good first boot as they may be all you need for summer climbing in the lower 48. If you start getting into higher altitudes, multiday trips above snowline, ice climbing, or winter mountaineering, then you'll need something warmer, stiffer, and/or with a removable liner.