You're right, there are a million papers on this and tough to tell how good.
This one looks useful. Bottom of page 52 specifically mentions 60 ATDC (300 BTDCf) as optimum DI SOI for maximizing MEP, which exactly matches Ford's 300 deg commanded SOI on the stock Mustang except at high rpm. I can only assume Ford pushed SOI up to 330 at high rpm for extra window. What's interesting is that the 2018 stock Coyote cal uses 300 for SOI all the time; it wasn't until 2019 that they started moving it as a function of speed and load. Page 53 points out that DI injection too early loses some of the charge cooling effect due to piston impingement. It seems as though the only real reason to inject before 300 would be if you ran out of time on the EOI side. Elsewhere in the article it notes that improved VE from GDI is due to the improved charge cooling (p.16 and 46).
https://core.ac.uk/download/pdf/4433861.pdf
I haven't been able to digest this extensive study yet, but it seems to be packed with info we could find useful:
https://www.osti.gov/servlets/purl/1253890
It does state that "Other than needing to be at 1450 psi and above, FRP [fuel rail pressure] was surprisingly not an important variable."
It would seem as though moving SOI to 300 at all times WOT, then lowering GDI pressure to push EOI back to ~90 BTDC could potentially net benefits in both VE and KLSA.