I can only speak for myself, but a large part of the appeal of S&S for me is the over-the-top visuals, the fleshy steamy visceralness of life worth living.

I find that with the cheesecake (and beefcake, let's allow for equal opportunities here!) removed, all you end up with is bog-standard D&D fantasy but with all the high fantasy hijinks toned down.
As has been discussed before, 5e does some things that really help for a S&S campaign, removing what in previous editions would have been obstacles. So let it be said that 5e is probably the best non-OSR edition of D&D to use. Especially with the great genre-appropriate setting info you get from the player's guide discussed here!
As for levels, well, high level magics pretty much removes every challenge appropriate for a barbarian in a loincloth. Fighting monsters can still be challenging, of course - but S&S monsters are particularly grounded, so even that isn't really a good match.
That is to say I agree with previous posters. Don't assume a Sword & Sorcery campaign goes on all the way up to level 20!
Instead, simply throw in all the demigods and epic monsters already when the heroes are single-digit level! Maybe not all of them needs to be bested in combat - they can also be fooled, bargained with... or simply groveled to, or you chuck them the odd virgin once in a while to keep them satiated! That's only honoring the cosmic horror aspect that is very much adjacent to Sword & Sorcery!
Take any random level 17-20 scenario and... just stop assuming the heroes are supposed to fight this thing, let alone win - and voilá, you have yourself a half-decent half-gonzo level 8 S&S scenario. Splash some mud, gore and supple flesh over the pristine four-color disneyfied presentation of modern D&D and you're good to go