If you decide on your serving temperature first and consult a co2 chart to find out your ranges you can make a start on deciding what methodology you'll adopt and this will influence your build. I keep my kegs at 7C which means gas left on at 12-15psi will eventually make my beer 2.2 to 2.47 volumes. This is the range that I generally work with. You don't really need to run higher pressures, but you'd require higher pressures if you kept it warmer, the opposite if you kept it colder, so deciding a serving temperature really influences on what follows. You then build your system to lose most of that pressure through resistance in the line before the tap to ensure a steady pour, too little resistance it'll explode out, too much the pour is very slow and frustrating. A compensator tap can be used to provide a little fine tuning if you want to build the system with a greater margin to accommodate the occasional beer where 2.2 to 2.47 isn't suitable. For beers that are lower than this you'll want to increase your serving temperature which will be fine for bitters and the like. For ones higher you'll want to decrease your serving temperature which will be fine for lagers and the like. For things in the middle that don't quite fit, for running different beers at the same time you'll want to build a more complex system with secondary regulators on one or all lines so you've got complete control. OR remember to turn your gas off between service and/or disconnect posts or fit non-returns between linked kegs.
See for most beers they'll gain a little or lose a little and that is fine because they all want to be between 2.2 and 2.47 anyway. I don't care if I put on a high carb beer because when the differential is very small the time to change is very long. They'll all eventually reach that range, but it doesn't matter a great deal to me. If I put on a really low carb beer which is almost never, I tend to brew to suit keg you leave the gas off between service and occasionally shut it off or disconnect the gas post on that beer only during service to allow it to run down a little. Good secondary regulators are quite expensive and cheap ones often lack the fine control required for the 1-2psi differences we are talking about.
A lot depends on what beers you intend to put on at the same time. What temperature you'll use for them because they'll all share that variable and how complex and expensive you want to make it. I've tried to build my system to accommodate a wide range of styles, but they'll always be the odd one here and there that doesn't suit it, but there are ways around it and the worse case scenario isn't really that bad anyway so I live with it. There are usually a lot of compromises though. What if I want to serve a lager and a best bitter with the lager at 3C and the bitter at 14C? Isn't going to happen with a kreezer. I'll serve both at 6C and swirl the bitter as I pour to lose a little gas.
I used to use set and forget (takes ages unless they are super cold, ties up limited space where a drinkable beer could be on, uses co2) I've used burst carb (great if I rack at 0C after cold crashing, 2-3 minutes to gas, rocking the keg, uses co2, bit dodgy sometimes) but I now prime them with sugar. It is cheap, easy, use a bit less for low carb, bit more for high and seeing as nearly everything benefits from 7-14 days conditioning doesn't slow down anything. I've access to a dissolved oxygen meter and co2 bottles sometimes aren't very pure, for things like NEIPA's I'm not sure I even want to burst carb them after taking readings on random bottles of gas.
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