You can still do the same, and it will work as before. Many P3dv3 payware addons still do this, despite it being against recommended practice. Any issues may come when P3d gets an update.
I use a dummy "P3d-user" folder and install into that, with the relevant paths added to the appropriate cfgs.
Works for most things, but some more complex addons (PMDG, A2A etc) may need to be installed into the real P3d folder.