Using the nano knock off version 32mhz LGT8F328P (purple one) on the arduino IDE. I tested the speed of the analog read and the fast mode digital pin toggle.
Hardware core and info. https://github.com/dbuezas/lgt8fx
From 500 analog reads in a for loop I calculated it completes one in about 23 micros coming out to about 43,478 samples per second at 12 bits. it's actually a little slower on the 10 bit setting coming back with 41,666sps.
With a for loop toggling a pin 1000 times using the fastio method I calculate each toggle to take 126 nanos. That calculates to about 7,936,507 times a second. But this was not verified by scope to see if the pins were actually switching that fast.
The digital test was thrown on just because of the crazy high speed the calculator says the PWM could go (like 250khz).
awesome calculator thing that writes the code for timers for you. (only works for this chip and the atmega328) scroll down and there is a link to run it from the web if you don't want to mess with installing it. https://github.com/dbuezas/arduino-web-timers/#mcu=ATMEGA328P&timer=0
there doesn't seem to be anything here