Adventure Cycling maps are great if they go somewhere that you want to go. They don't always choose the roads that I would so I sometimes deviate from them in places. I often pick up a paper map for a state as I pass through. Some states have really good bicycle maps. Some have good regular road maps. Google maps is a good way to supplement or check out a possible alternate route.
The ACA seems to choose to go out of their way at times to either hit scenic roads or roads with less traffic. Often to me it looks more like they go out of their way to climb a huge hill with no real advantage. I tend to avoid some of those and take a more direct route at times.
I tend to like routes with the US designation like US-90 on the Southern Tier. I rode it in places rather than ride the roads that the AC maps chose on the ST. I think a lot of folks rode US-90 for a while east of Van Horn TX because I met other riders doing the same as I was. There were also places where I rode the interstate highways (roads with the "I" designation like I-10) a bit more than the ACA chose to.
I have sometimes thought that riding US-90 for most of it's length wouldn't be a terrible way to go. I think that starting out with the ACA ST maps and being open to trying a bit of both would be a decent way to go.