@SirDAN thank you so much for this! Unless I find myself doing some crazy climbing rides, I think a Race Helix (9-45, not the 9-50 or 9-52) and a 38t chainring should give me more than enough gearing for my east coast riding while still maintaining a similar top end (38/9 is very close to 40/10).
According to the eThirteen site the Race Helix does work with flattop chains and, at least for now, do not plan to get an Eagle AXS derailleur. If I go that route I might just go all in on Transmission, but I’ve already spent enough money this weekend. 
Again, thanks for the help!