which microcontroller should I use for my project?

Hi,
I'm fairly new to microcontrollers and have read multiple guides, although still asking the question.
I have used Arduino for quite a long time and have developed some product concept. I am only 14 years old though.
I am currently developing a wearable project, therefore size, weight, and battery are huge constraints.
My project will include; Touch OLED, Gyro, IR LED and receiver.
As I have used Arduino, I am quite familiar with the Arduino offset of C++.
It will be appreciated if the MCU has example codes/ others have used similar components.
Could you please help me on both; hardware and software.

Thankyou in advance.

It's like this a lot of people get hung up on the Arduino because they can't see that just because you use a uno to test code and ideas out with you don't need the big old uno to make your finished product. You can make a board and use just the chip
That chip is small and you can program it with the same code you used on the uno and make a small PCB to hold it it can even be used with slower crystal or none. I would stay with arduino.

"Just the chip" huh?

You can use the ATmega328P by itself without the Arduino and still code it in Arduino IDE if you're already familiar with the Wiring programming language used by Arduino. Matter of fact you don't even need the boot loader. The Arduino IDE will work with the USBtiny ISP programmer, which you can get dirt cheap from SparkFun.

https://www.sparkfun.com/products/9825

Although with a bare AVR chip you'll have to learn how to set the fuse bits, which isn't too difficult to do. One useful forum for learning low level AVR stuff is the AVR Freaks forum -

https://www.avrfreaks.net/

He has a programmer if he has a uno so all he needs is the uC

Oh that's right the IDE comes with Arduino ISP in the Examples.