I am starting a brand-new build of a M-Track layout, and the board work is completed so I am looking at how to start the top side. I am curious what is the best way to go for the top side?
It will have mountains, tunnels, river and seaport.

I have seen people in videos using a 1" or 1/2" thick piece of foam board so as to be able to cut out the water ways and start the elevation of the mountains by easily adding more layers of foam board to shape. What are the pros and cons of foam board?

I have also seen people just use plywood and fill in around the track with foam board or chicken wire and madge podge.

What do you experienced scenery builders recommend? There is so many different ways to build what's the good bad and ugly.

Hello tandrschaefer
Not a landscape specialist here but here are my thoughts

Method 1 a nice and quick method is to form landscape using a metal mesh like Noch 60990. This is sort of a screen in aluminum (you can cut it with scissors and install in place with little nails or hot glue. You may form the landscape with your fingers exactly the way you wish.
When finished, you cover with one layer of plaster band and make it realist with the finger.
You may add "rocks" with plaster just before it sets up
Then, you paint the landscape using cheap acrylic paint
Then you insert a screw and use an electrostatic machine (I use the Noch one but I started using an "electrostatic fly killer" coupled with a cheap metal skimmer.

This is the method I used on my layout. The result is incredibly solid, light (1-2 mm thick)

Foam method Another method is to use expansed plastic foam (I would avoid Styrofoam) but you MUST have a hot wire cutter to avoid having huge quantities of litthe electrostaic charged that are really a pain to clean. Advantages: very light and sturdy but takes a lot of space

I am more focused on the automatic operation but here is what landscaping becomes with roads and trains
So I jumped from a bare-bone operation (3 levels, 10 mm plywood, frames and PC operation using Rocrail)

to landscape with paper masonry (walls), electro-static grass machine, acrylic paint, metal mesh, plaster tape, led street lights made of earbuds tube and Christmas tiny LED lights

Cheers
Jean

Thank you for the advice I have never done what you are suggesting but will give ita try and see what happens. I appreciate your time to comment.

I used Woodland’s Shaper Sheets for all hills and mountains, and I would do it again. It’s a double-layer sheet made of thicker aluminum foil on one side and and fabric on the other side. I add a link to Woodland’s presentation of the product, however, you may as well use no-name standard model plaster. I combine the sheets with plaster rocks made with different rubber molds. You can see the result in my layout thread, note that I’m no expert in landscaping (link in signature below).