Shrinking BluePill?

[Koep]

Hello All!

I am thinking about testing an idea for motor control where I'd need a pcb smaller than blue pill.

Which functions/functionalities in Roger's core stop working if I omit the
32khz oscillator
reset button
boot pin headers ?

I need:
timer1
adc
hardwareCAN
few IO's

Programming with st-link/SWD is OK

I was looking at the pictures of the WeActStudio BluePill+ and both schematic and photos show much
smaller component count. the bottom side of the pcb is empty ( as is with the F4 black pill)

Researching this I read that the internal oscillator inaccuracy is the reason for the external 8Mhz crystal.

How inaccurate can the HSI be? Enough to impair or to risk impairing CAN bus comm?

Is the inaccuracy a difference between MCU's or is it inconsistent/wandering frequency in one MCU?

Rgds,
Tapio