99% of the time, the sort of flights (I presume) you are talking about, will be vectored on to the final approach track.
The main reasons for this are:
1 - It enables us as atcos to give the aircraft the most expiditous approach to the runway in use, without having to put them into the hold.
2 - It ensures that there are no significant delays to departures as well as arrivals.
The problem with visual approaches is that they still have to be treated as IFR flights, so if an aircraft declares that they are able to continue visually, it is often more expeditous to vector them onto final approach in the normal sequence, rather than let them do their own thing.
Whilst we are doing the above, it gives us a better chance of slotting in VFR flights in between IFR flights, purely because we know where everyone else is in the sequence and can regulate them accordingly (it may not seem like that, but I assure you it is the case!).