This has been a problem since day 1 on most model railroads. Let's start with what most have in house and go from there. First, looking at most layout books, you will note that it is built on a sheet of plywood, only because it is a 32 square foot unit which is dead smooth, with no jumpy sections between boards to make up the thing.
Next is the problem of what to do? Let's face it, an "all in one" layout is going to be a massive bowl of spaghetti track work. How long will your attention be held with one train chasing it's collective tail, the same cars around the same loop, 4 x 6 or 4 x 8? Even with spurs it is still doing the same thing. you need to get the train to go away and another one to come into play as it was.
So depending on what you in the end want to do with your pike, you need to decide if it is going to be a long run tail chaser, or a short run switching affair. Looking at over 30 years of train layouts, you end up with either one or the other - not both in one 4 x 8.
What you need is more space. A second 4 x 8, or start building a shelf pike is the next step. Both depend on how much real estate you have gotten for your pike. If nothing else, make more room, like I am currently doing by cleaning out the house, junking old stuff, and in general clearing out the place. this give you two things. First a cleared out house which doesn't look like you are a hoarder, and second that feeling that anything is possible if you only applies yourself to the task. Trust me it does.
NOW that you have more space to run, make one 4 x 8 the long run, and the second 4 x 8 a switching area, and connect the two into one big pike. OR tear down what you have now, and start a long shelf pike with all the things you really want from the pike on a long, very long shelf.
Back in the 70's I had most of the basement to myself, and built all over the place. Economic changes in the country forced me to move the biz home. This meant the pike had to go out and the biz move in. It is now 25 years later. I am now cleaning out the final mess of the biz and other stuff down here which we no longer need, while retaining the essential parts of it to keep on working, and moving the pike over there into that now cleared space.
Planning this in the early 00's I knew I could not do it all at once, or have a do it all pike on one board. This was a given. SO do what I could to make it a multi phase build, with the future in mind, but not yet on the ground. If you go back over my posts, you will note that on the original Woodland Scenics pike, there was a very short stub with a bumper. this was meant as a handle to connect eventually with another board.
In this record photo of track work / scenery fixing you can see the actual stub below the Husky car. This did change when I added the new yard, but it shows what I had planned from the start.
In time I did make the next expansion, the yard and engine service facility. Now I had two parts of a major pike. A 4 x 8 long run 3 times around going up and down fully scenic ed, and a yard operation. This meant I could make up and break down rains, while making one sit some place and hide while I was working the other one. Not the best, but will do for now.
This will give you an idea of what I have been doing down here. The new board will go right where the caboose is now. It will be a two foot overlap and extend down to the bottom 8 feet. This shows phase one, the River Pass behind, and the yard extension on the front.
We are into the third phase as I write this. I am building another 4 x 8 - only this is not a total 4 x 8, it will be in effect two 2 x 8 shelf units stuck together on one board, with a ridge between them, and enough room to move around behind the unit to work the back. The interconnect will be a two foot over lap on the front of the switch yard and the edge of the second board. You will see when I start the build photo work.
This gives me a total run of almost a mile and a quarter of HO track (scale) and three to four minutes between times when the train rumbles past one point and the next time to comes in to that same point, covering the total of two outside runs of two 4 x 8 boards.
Meanwhile, there is switching going on on the second board, serving industry and a intermodal yard. The old main yard will also be in action as it was added to the front of the original long run.
Yes you can have it all, but in time. Not all at once, and not on one board. there just isn't enough room to do justice to everything you want to do and scenic the thing so it doesn't look like a plywood central.
For now, as you start, you can use the all in one for awhile - but you will get tired of it quickly, and want to build more. Enjoy the hobby, once the railroad bug bites, you will find it is a fatal disease. It will consume you for a lifetime.
Enjoy the hobby!
The Aerojet