starting with Chapter 1:
I did a bit of testing today and found out that you can get a shiftboost on a little hill on the right at the very end by MTSing into it and exit it with a sideattack (maybe even without, with more speed) on boostlaps.
I tried to get a double shiftboost there, but I couldn´t get one so far, but it feels like you can squeze another one there, maybe just by going faster, but I will try this excessively in the actual TAS.
The important part of getting one shiftboost, is not only that you go faster, but also might be able to get another shiftboost that you couldn´t get otherwise and keep going faster.
The faster you go, the easier it is to get more shiftboosts.
Regarding the capsule collection strat you want to get the inner ones in the opener and take all boostplates, as you aren´t going fast, because you have no boost. Also I might take advantage of this little trick
https://youtu.be/tj22kPQeFYM?t=122 to go faster between the boostplates, but it can´t be abused too heavily, because it slows you down after a while.
Regarding the TAS:
I will wait a little before starting the actual TAS, because I want to make it on a more recent version of dolphin, but the current versions still have that issue when advancing frames.