(SOLVED) Fast HW check: (18 digital + 4 analog to I2C ) Arduino Mini Pro + MCP23017 or STM32? Arduino Mini Pro+MCP23017 or  STM32

I want make device, which reads 17 digital buttons and 4 analog, process it somehow and send the result to I2C bus. Also there is a LED to be managed. I may want to attach some wireless too later, but I am not really sure, if I woud do it (which would need 5-6 mor digital pins). I need to update the firmware often, as it is under heavy developement just now. I should make the PCB as soon as possible, but programming can wait some time. 

The PCB would have buttons and analogs on it (and MCP in the arduino case). Also lot of connectors, like I2C, programming interface and some power regulators, the LED (or maybe more of them, if there was few free pins, but it is not mandatory). The processor will be connected via wires for space reasons (and maintainability and the board may be redesined later), so only long row of soldering pads on PCB for it.

Main decision:
If I opt to Arduino, then MCP will be part of the PCB and connected to I2C bus, if I use STM32, no MPC will be present and buttons would go directly to output connector.

Making the HW is no problem for me, the logic inside is also easy (basically read all inputs, normalize analogs to some range, make some simple tests and if desired, send result over I2C. Reply to some simple I2C too.)

I have a lot of Arduino Mini Pro, but it is few legs short for the task, so I would use MCP23017 expander for 16 of that digital buttons.

I also got some these STM32 
https://www.aliexpress.com/item/STM32F103C8T6-ARM-STM32-Minimum-System-Development-Board-Module-For-Arduino/32279776568.html but did not open the package yet. Anyway I want to learn to use them "sometimes soon".

Maybe it is just the kind of starter project, which I would like to do.

Now I am just not sure about the number of available pins on the STM32, on first look it have more pins, but each description I found yet states too much details about additional functions, but I got confused about the basics here. So my question is:

Can mentioned STM be easilly programed as Arduino, manage I2C communication, and still have comfortable 18+4 I/O pins free? And 23+4 I/O free?
Can mentioned STM be easilly programed as Arduino, manage I2C communication, and still have comfortable 18+4 I/O pins free? And 23+4 I/O free?


it can be programed as Arduino, manage I2C communication, and still have 18+4 I/O pins free or 23+4 I/O free.

it is only knowable to the person programming it whether it can be done easily or comfortably.