Amazfit smartwatches are made by Zepp Health Corp (formerly Huami Corp), a health technology company. Zepp Health has a historical and ongoing relationship with Xiaomi as a manufacturing partner and exclusive wearable provider for Xiaomi’s fitness products, such as the Mi Band series. Huami developed and manufactured many of these devices and also offers its own brand, Amazfit, while also collaborating on the Zepp Life app (formerly Mi Fit) for managing Xiaomi devices.
There is a list of Amazfir watches from 2016 to 2024 on r/amazfit which may prove useful.
The Amazfit BIP 5 (Aug 2023) uses the Sony CXD5605, according to the deep dive teardown by TechInsights in Mar 2024.
The Zepp app does not provide a FIT export. It has yet to be confirmed if the GPX or TCX exports include the Doppler-derived speeds.