I would think its 16-bpc. That is what Adobe uses and I assume most RAW converters use a container space of sorts, that is 16-bpc, while most RAW files are 12 or 14-bpc. Most TIFF’s are 8 or 16-bit and JPEG’s are 8-bpc.
Which ever one you import I think internally DXO PhotoLab adopts. In case of Tiff that is 16 bpc and RAW it will work in 16 bpc. In case of 8bpc JPEG I think it will stay in native bit depth.
If you are confused about bit depth, Many years ago I made an indepth tutorials about everything you never wanted to know about bit depth, pun indented. It should explain everything you might be interested.
Bit Depth in Depth: All you never wanted to know about bit depth. “Lost Tapes” series
