Hi, Marineimagining,
The two issues are really not the same thing, which is one reason for confusion. Not all recoil operated guns have locked breeches; they could be operated by gas or by a delaying mechanism. The goal from a design standpoint is what is achieved - the delay in opening the breech until the pressure drops - not how that is done.
In theory, a fixed barrel gun would be more accurate than a gun with a moving barrel, but in practice the difference is often too small to matter, so the benefits of the locked breech, in terms of less mass or less expensive mechanism, will sometimes outweigh the problems.
Jim