I don't think it would work like that, but you'd go to the ACP and mess about with the classes in Manage Categories, to me, that looks like col-md-9 for announcements, and col-md-3 for the rest.
Bootstrap works in 12s. So This forum has 3 columns, so each is set to 4. 4x3=12. My site has two coumns per row, so I use 6. 6x2=12.
Then if you want to show the latest topics, to the right of the column class in Manage Categories, is a "# of recent replies" field, just enter a number in there.
The issue you may have is that bugs may not appear until AFTER the announcement window (you'll have a large gap after comments and bugs may appear under announcements)
Screenshot for reference:
Site is in my signature if you wish to compare.