Hi, i like share the low sound fix for the Teclast X98 Plus II. I saw it for the Pro, i can confirm that work fine in Plus II with Win 10 Aniversary update.
To fix, only download Surface 3 drivers from Microsoft, download this file Surface3_WiFi_Win10_161250_0.zip
https://www.microsoft.com/en-us/download/details.aspx?id=49040
Extract the zip and the driver to use is in Drivers/Audio/HdAudio
Install its easy, only open manage devices control panel, choose Intel SST Audio properties update driver. And then, Local search / List of controllers / Disk option, choose the extracted HdAudio folder to search in.
Hope this fix help you.