HOW IFC IMPORTS
IFC is a so called 'data exchange' format. There is no specific IFC software that creates IFC format files.
When IFC is imported into any software it is converted into that software's format. So when you import (or link - see below) an IFC file it gets converted into Revit objects.
Unfortunately these Revit objects are really crappy and uneditable. Usually the only editing possible is to delete elements. None are parametric as IFC does not support parametric geometry, even though IFC objects have parametric values.
It is also difficult to control visibility as objects may not be normal Revit categories or subcategories, and materials are unique to IFC components (for example every face of every object may have a unique material).
At best IFC imports are only useful as a geometric placeholder, at worst they are unreliable as elements may be missing.
AVOID IFC IMPORTS IF YOU CAN
(Note that this depressing situation may improve, so it is worth testing
INSTALL IFC ADD-IN
New IFC add-ins for Revit are regularly being created and updated. Before doing an import or export make sure you are using the latest add-in.
There is an open source Add-in, also from other software vendors including; Graphisoft (ArchiCAD), Tekla, GeometryGym
Otherwise search the Revit App store for IFC Add-ins.
IFC SIZE
If the IFC file size is large try reducing it by using the free Solibri IFC Optimizer.
LINKING IFC FILES
Revit has a command to directly link IFC files. This basically creates a new Revit file contained the converted IFC model, which is then linked in.
You can open the created file and make edits if required. By edits I mean you can delete things.
SETTINGS
If you do not want walls to join automatically clear Auto-Join elements when opening an IFC file.
Also try this if you are having problems with a large IFC file.