Decided to issue a PR with my current stuff:
Unor4 timer period updates by KurtE · Pull Request #116 · arduino-libraries/Servo (github.com)
I now have it reasonably working with AGT timers. This required some fixes to the FspTimer code.
PR for that:
FspTimer does not initialize properly if AGT timer is selected. by KurtE · Pull Request #120 · arduino/ArduinoCore-renesas (github.com)
I think I am done playing with this for now.
Kurt