Whenever I play slide guitar solo (unaccompanied) I use open tunings. Usually Open A or Open E.
But I thought I heard a long time ago that blues legend Muddy Waters (ne’ McKinley Morganfield) recorded some solo slide guitar in Standard tuning. I know he played slide in Standard when he had a band behind him. But that’s different: playing solo, you have to play the backup too, which is hard to do in standard.
TIA.