Google to date has three smartwatches of its own that are not Fitbit, namely the Pixel Watch family. The first generation uses an Exynos chip then the second generation and the latest Pixel Watch 3 uses a Qualcomm chip. In the future, Google may also use Tensor chips for their smart watches.
Google is said to likely start using Tensor chips in 2026 for the Pixel Watch 5. The chip configuration is said to contain 1x Arm Cortex-A78 and 2x Arm Cortex-A55 cores which are arguably outdated. However, this does not prevent Qualcomm from presenting a powerful efficient chip Snapdragon W5+, where it uses an older configuration which is Cortex-A53. Google will probably use 3nm design in parallel with the new Tensor chip for the upcoming Pixel phones produced by TSMC.
Using its own chip in the watch means Google will have more freedom in terms of providing software updates, adding new features and functions and promising longer durability because everything is under their control. Anyway, let's all look forward to it.