I think a COB is just that- only the current owner info, include what you want or make a distinction between a COB and a COB/plat info. We have to keep in mind that those that request this kind of search is a way for them to keep more of the "full" search money for themselves and short change your work. If they have a policy, then all the need to complete a "full" search is the current owner update and a copy of the plat- It's ok and well within their prerogative to do that, as long as we, as abstractors and the ones on the E&O hook, be sure to note that the COB/plat is "only" that and not a full search. Just be careful to cover your liability aspects. I deal with a company doing mostly commercial cases that requests current owner  or 40 yr searches and when I have completed that they come back after a while requesting additional copies of docs that are mentioned in the last deed of the search. I have to tell them to ask for what you want- if you want 20, 40, 60 or 100 yrs, ask for it, but please don't have me going back a month later to review the case to get something from before the requested search period.
As for M&B descriptions, I will always plat them out and include that with my cases to verify the descriptions. When doing M&B cases it just is too easy to make typo's or leave out , miss a line.I have found most of them contain errors from the original  description.This also is a way for me to take the exception in my front sheet to that error and suggest a survey.( which can be pushing them - but shifts the burden to that possible problem)