The strengths and weaknesses of different types main line arrangements are:
Point to point.
Pro: This is exactly how real railways look.
Con: Unless you have a long narrow space, this will either give you a very short mainline run or an extremely crowded plan, perhaps with steep grades. Both terminals have to be approximately the same
size, as they have to receive all traffic the other generates. No continuous running.
Recommended if you have a suitable space and know this type of layout if perfect for you, or if you have very little space, so a pure "switching" layout is what you have to build.
Out and back.
Pro: Gives an opportunity to model one large terminal with extensive operations, or a smaller one with space for realistic scenery, as no other track has to crowd close to the terminal.
Con: Takes up relatively much space for relatively little main line running. No continuous running.
Recommended mainly for medium or large layouts, or for a small layout where the terminal is the whole layout, perhaps combined with a removable sector plate.
Dogbone.
Pro: Permits lots of mainline traffic to be run, as there doesn't have to be on-layout destinations for any trains. As the trains are easily turned, it's suitable for very dense traffic.
Con: Takes up a lot of space if you want to have much of the mainline visible.
Making room for two reversing loops is a headache in s mall spaces.
Recommended if you want to run many different trains and have plenty of rolling stock.
Oval.
Pro: Can be built very compactly. Has continuous run capability. Lap running can make the single station do the job of two or more. Built either with lots of scenery or track.
Con: Doesn't look very realistic, does it? A stretch of the mainline has to be hidden, either in a tunnel or behind a forest or buildings.
The type of layout I recommend, unless you know must have another, as it is the easiest to extend, either with more tracks in the same space or with an addition.