What does this mod do?

With this mod you can not create landfill like you're used to, instead, you create 'Land mover'. With this tool, you can dig up land from your world (use like landfill, but on land instead of water). This results in a body of water and a piece of landfill as you know it. You can place that bit of land elsewhere.

I still want to be able to produce landfill the 'old' way...

For you I've made a setting. You can enable the landfill recipe again in the settings while creating your map.

I cannot place down the compressed landfill?

The function of the land mover mk2 and the compressed landfill is that you can gather landfill more quickly, store it more compact. If you want to use the landfill, you'll have to decompress it first. There is a recipe that converts the compressed landfill into regular landfill.