I watched the third video you posted, which deals with the speed. Very informative and thorough. Comparing his numbers with our plane in AH, it is clear that we have the Ki-84 with the -11 engine, not the faster -21. It also shows the AH version is historically accurate for the -11 engine. So we do, in fact, have a pretty accurate representation of the plane.
Now the question is, which version was produced more and/or which version saw more combat? That might make the case for keeping the -11 engine or changing it to the -21.