I don't know
would Borg have such a forehand with modern equipment? I thiink you can only say whose achievements are better/more impressive. Who would beat who is just too hard because of big changes every generation(hence I quoted AJ in that post).
AJ also says all greats would find a way in any era, I dont fully agree with that statement (Rosewall and Mcenroe would not find a way in the modern era, even Sampras doubtfully would achieve much, that is what I think atleast). However, I see absolutely no reason to question Borg's ability to learn a great forehand with 90s raquets or modern raquets, ofcourse it would be great and he would love to play in the modern grinding era of the 2000s, even if Djokovic and Nadal probably would give him a hell of a fight.
Anyway, Borg would beat Courier in any era on clay, that much I can say without any doubt.