Modified Cross-US Route?

Looking for some advice as I plan a cross-US trip. This is a bit in the future, and I plan to complete a modified Atlantic Coast tour in segments first, based from my home on the East Coast and using Amtrak to break it into smaller bites around work and life.

Anyway, I want to eventually complete a cross US trip, heading E to W. I've looked at the ACA maps, and read a lot, and it seems like each route has their pros and cons:

• North Dakota and Montana on the NT being dangerous re: traffic

• Ohio/Indiana/Illinois on NT being boring.

• I wonder about the MO to Western KS stretch on the TA being similarly boring

• I've heard that Glacier NP is amazing (especially the Road to the Sun).

• Minor: dogs in Western VA and KY on the TA

I also just kind of want to go to Niagara Falls on my bike, even though I've been before via car.

I've sketched up a rough route map, borrowing from TA, NT, and Parks and Prairies mostly, trying to hit up scenic areas/avoid others. The end spot isn't set in stone, just somewhere on the West coast (I'm not too bothered about actually dipping wheels in a sea/not bay unless there are better start/stop points). I also figure it'd be nice to take the CO + GAP out of DC (get there via Amtrak) as a start to a tour, to ease into something so big (note: I know the map currently doesn't follow these trails). Are there any general thoughts on this route? Am I overblowing cons to the NT and TA? Is the infrastructure of the TA worth it for the portions that are slogs? Am I missing some super scenic place just off-route, or routing to somewhere that isn't actually all that impressive (I've been to Zion and Grand Canyon NP, and would like to visit more).

I appreciate any and all advice!

https://cycle.travel/map/journey/876638