> If the code is heavy on FP-code or bandwidth use a G5, if it is
> AltiVec use a T4.

AltiVec on a 2.7 GHz PPC970 may be faster than on a 1.8 GHz e6500. And are you sure that bandwidth of PPC970 is better than e6500?

> I have only tried to put the CPUs in relation to each other ...

Already done long ago:
https://morph.zone/modules/newbb_plus/viewtopic.php?forum=3&topic_id=7001&start=743

> How do I know that the code is G4 optimized? Because for a long time
> it was the only CPU in Amiga land available ;-)

For an even longer time, G2 and G3 have been used in "Amiga land". So it may as well be optimized for one of them.

> It surprises me, that everyone is surprised about the performance
> of the NXP offerings ... who in hell has really thought, that a T4
> is as fast as the latest Intel offerings?

The comparison was with a decade-old Motorola/Freescale offering, not with any latest Intel offering. That's worlds apart.