John Cutler
It would be useful for us to know what era you are modelling.
For my own part, I model the 50s-60s BR period in the South West. The Southern and BR(S) kept their coaches in fixed sets. I therefore use fixed hooks to maintain them thus and have auto-couplers at the ends of the sets only. This means there is no problem in having to allocate/schedule separate locos for passengers and freight traffic. If you do not plan to split coaching stock then you can apply the same strategy. You only really need to split rakes a lot if you model a main-line terminus, carriage sidings or carriage works.
For older non-gangway coaching stock, I use Brassmasters lost wax castings for fixed hooks (£8 each); look them up in the Rolling Stock section on their website. These follow a design by Pendon and you can make your own variation: see the 2 designs in Iain Rice’s book “Railway Modelling the Realistic Way” (page 340).
I confess that I only have one gangwayed coach set and that is a 2-coach Maunsell pull-push unit by Hornby. I use Roco’s fixed links (code 4490) upside down for that because they are slightly shorter than Hornby’s own but are compatible with Hornby. The coaches end up so close together that the corridor connections really do not need replacing -see my post on converting this pull-push set. The downsides are that separating the coaches is not straightforward and storing the units can be difficult. Fortunately I do not believe I will ever need an 11-foot cassette to store a 12-coach fixed rake! Hornby’s centring NEM pockets allow tight radius curves to be navigated but the rake looks ridiculous on anything other than fairly straight track because the corridor connection ends fail to align realistically. Having said this, the pull-push unit looks OK navigating a B8 turnout on my running line loop.