There is some confusion here and I'm not sure if it's you or me. You are certainly more up to speed on PSOC4 than me. Correct me if I'm wrong.
We are discussing using a built in inverter with external crystal to implement and oscillator because the PSOC4 don't have a dedicated oscillator. I don't see where PWM, external oscillator, or any of these other things enter into it.
The PSoC 4 has a 48 MHz internal oscillator built in with +-2% accuracy.
You can also feed and external clock up to 48MHz on pin 0_6 to drive the chip without using the internal oscillator.
You can't drive an external crystal directly but it will take an external oscillator up to 48 MHz at only 1MHz increments.
You can use an output pin as a driving clock that is fully programmable and you can change the frequency using the internal or external oscillators with 16 bits counters and dividers so you should be able to achieve any target clock you wish.
It also has lower frequency clocks on the 32.768 KHz fixed range for an external low frequency clock, aimed at a precision timer. the built in low frequency clock has a lot of error but can be trimmed to a +- 10%.
I have yet to play with the analog outputs or the derived internal digital clocks.
And to answer westfw, the answer is no, it only takes a single high frequency oscillator but you can't drive a crystal directly. Unless the clock driven output works then maybe it can drive an external crystal directly without the need of an oscillator.
Edit: but if the external oscillator is accurate enough, you can derive internal clocks from that, I believe up to 8 or 16 clocks can be derived, will have to look at the details, but definitely can derived 2 clocks from the main clock.