I tested files at all relevant sample rates and as best I could tell (listening and measuring) with the Bifrost MB (O18) it was doing 8x oversampling.
The Bifrost MB (O18) was a quite close, overall, to the Gungnir MB (OG) with it really only being micro-dynamics and and low-end weight that the Gungnir MB (OG) was ahead - at least if you stuck to comparing the single-ended outputs (Gungnir MB (OG) had a resolution advantage via its balanced outputs).
Bifrost MB (O18) was closer to Gungnir MB (O18) than Bifrost MB (OG) was to Gungnir MB (OG) on technicalities, but Gungnir MB (O18) had a leaner, drier, more forthright presentation which gives it a rather different signature compared to both the OG iteration and the Bifrost MB (O18).
I plan on reviewing the Bifrost 2 at some point, though it won’t be before October. Doubtful that it will include a direct comparison to earlier versions of Bifrost MB (either OG or O18), however, as I don’t have them available.
*(O18) = Unit built in October 2018. (OG) = Original Release.