Equities aren't real capital, in the economic sense, either. Real capital is land, plants and equipment; equities are financial capital.
>"the Swiss National Bank digitally printed an enormous amount of Swiss Francs and bought Euros in order to peg their currency lower (didn't work)
What do you mean it didn't work? They maintained the peg for years. One of the reasons they unpegged the currency was that the Euro was depreciating, thus maintaining the peg was causing the SNB to depreciate against other currencies, like the USD.
>what is the fair market price of global equities when some buyers can print money? Does it matter?
There's no mystery. Fair market price is the agreed upon price in a transaction. If you think that for some reason all prices are distorted due to central bank printing, then account for that distortion in determining what price you're willing to accept or bid.