Hello,
As always, there is no generic answer to analysis questions without a better understanding on our end of your research questions.
- But broadly speaking, it always recommended to remove the DC offset from raw MEG recordings, as these DC values are much larger than brain signals and high-pass filtering will cause use artifacts at the edges of the recording, which will spoil your analyses, especially if you epoch the data over shorter segments.
- No need for channel interpolation if you focus on source mapping.
- Brainstorm will take care of removing the BAD segments from further analyses.
- If you're looking at resting state, you can indicate that the data covariance be derived from the entire recording. If you do not have empty-room recordings, the noise covariance can be set to Identity (no info on noise).