I’ll take this in parts:
Getting additional FP+… some rides will be easy, some not so much. Forget about getting SDMT, so no matter what strategy you use, it must always be one of your first 3. Rides like Pooh (which I don’t see in your itinerary but is fun), Little Mermaid, Haunted Mansion, Pirates, Jungle Cruise will be pretty easy to get the additional ones for most or all.
Comparing Plan 1 vs. 2… yes, I can see what you mean. The two main causes of the disparity that I can see is the 15 backtrack time from SDMT to Splash, and the 14 minute wait for SDMT. I can’t dispute the 15 walking time… but a 14 minute wait for SDMT, WITH a fastpass, is not likely. This past May, we did SDMT on a much busier day, also with a FP+, and including the ride itself, we were in and out in under 12. Even taking that away though, the two plans clearly show you’re better off with the first in a vacuum. I would just add that the current wait times for both plans seem low, and any increase would make the advantage of additional FP+ really valuable.