Are these identical?

In value, yes.

The S on the right appears to be bold, doesn't that make it a variant? Large/ small date etc?

Die letters on US coins are not considered variants.  In 1968 the mint letters were added to the dies by hand. A mint worker used a stamp of S letter and a hammer and made the S in the die. A heavy hammer blow went deeper so the S looks bold. The next die had a lighter hammer hit so the S looks lighter.   So not a variant. That year had only one size date.