If you go with two FF programs (with one of them being AS), then it would seem that you are looking at one or both of the following strategies:

a. The second one is just to collect miles from flights where AS and its many partners do not have a reasonable flight choice. In this case, the only reasonable choice if you are flying mostly US domestic is a Star Alliance carrier like UA (or US or AC), since AA, CO, NW, and DL are already covered by AS' partnerships. (This is ignoring the FF isolates like WN, B6, F9, FL, etc. which you might as well open accounts with if you end up flying them, but do not factor into the decision you are asking about.)

b. You expect to be able to gain the desired level of status on AS and another airline, with the other airline's status being more useful than AS status for non-west coast trips. In this case, AA, CO, NW, or DL may make sense as a secondary program, despite the apparent redundancy with AS, if status and awards there is more useful for some of your flights than AS status and awards even with the AS partnership.

From what you write, it looks more like (b) above. In which case, checking the schedules and flight options to your likely destinations, as you are doing, is the obvious step to take in deciding which FF programs to choose.

But note the rumored mergers going on (US/DL, UA/CO). If any of them go through, that may affect FF alliances and partnerships.