To commit/collapse/flatten multicam (ie replace multicam instances with source clips but keep any effects applied) select clips, right click & ‘multicam|flatten’
To disable multicam (ie prevent camera switching) select clips , right click & deselect ‘multicam|enable’
To disable multicam viewing in program monitor (ie to see just switched line cut instead of line cut with multiviewer) use wrench icon on program monitor & select composite.