FreeCAD lets you do parametric modelling and well as seeing all of your changes while you're making them.
OpenSCAD is constructive solid geometry and you write a script then render it. You can essentially only create STL geometries with OpenSCAD, if you just plan to model and 3D print single parts OpenSCAD might be sufficient, anything more complex, particularly assemblies with multiple parts and you'll need a different CAD platform.
In general parametric modeling is far more popular it's how solidworks, onshape, fusion360, etc. work.
OpenSCAD is constructive solid geometry and you write a script then render it. You can essentially only create STL geometries with OpenSCAD, if you just plan to model and 3D print single parts OpenSCAD might be sufficient, anything more complex, particularly assemblies with multiple parts and you'll need a different CAD platform.
In general parametric modeling is far more popular it's how solidworks, onshape, fusion360, etc. work.