This request is actually pending on Nik accepting DNG files. When this happens, Photolab should have the option to choose TIF or DNG for export, with the options listed above, I do not think that a discussion about Photolab’s integration with Nik belongs in the Nik forum.
The request to support DNG is currently being voted.
The advantage is that DNGs produced by PL appear to be more compact than TIFs, and DXO already supports output to DNG with just optical corrections and denoising (HQ, Prime, DeepPRIME). A workflow via DNGs is the preferred route if multiple images are derived from a raw file. The long process of demosaicking and denoising is performed once, with optical corrections saved to a DNG. From there, a user could continue editing in PL, or invoke external programs accepting DNG. For example Picture Window Pro 8, Microsoft Research ICE, Snapseed … and hopefully Nik collection.