What is the difference between weit and weit entfernt? Which (if any) is the correct version?
Er wohnt weit von mir.
Er wohnt weit entfernt von mir.
Actually, there is a difference.
Weit is not commonly used for distances (i.e. in the sense of "far") without being accompanied by "entfernt" or "weg". weit standing alone can be used for clothing, meaning a wide fit, or for a wide landscape (i.e. in the sense of "wide", a close relative).
Er wohnt weit weg von uns
Er wohnt weit entfernt von uns.
Both meaning "He lives far away from us"
but:
Ich habe abgenommen. Jetzt sind mir alle meine Hosen zu weit.
(I lost weight. Now all my pants are too wide)
or
Nach dem Wasserfall öffnet sich die Schlucht weit zu einem See.
Beyond the waterfall the ravine widens towards a lake.
The following two sentences are correct. They both express a geographical distance.
Er wohnt weit entfernt von mir.
Er wohnt weit weg von mir.
In your first sentence, Er wohnt weit von mir, I am missing something. It's not wrong, but I would like more context. It could be a geographical distance, but it could be also a poetic expression of an emotional distance between two persons.
Actually there is no difference.
I think most commonly you would use:
Er wohnt weit weg von mir.