The MCU on the watch is marked RTL8762CK.
One seller listed the "G-sensor" as STK8321, which is a "Digital Output 3-axis MEMS Accelerometer" featuring I²C and some interrupt pins.
I also suspect the heart rate sensor and touch screen to be I²C devices.
The LCD is marked, but a search on the internet doesn't yield anything of relevance. The watch is advertised to have an 1.3 inch240x240 IPS LCD. It's connected via 18 Pins and a quick analysis with the scope showed bursts of 5MHz square waves packages on one signal, indicating either SPI or parallel bus. Maybe it's a ST7789 controller.