She is in Athens and does tours there. She can arrange a van and tours to Delphi IIRC. Email her and ask for what you're looking for.
If you are going to be in Napflion/Myceanea I would reach out to katerina.dize@gmail.com. We had a tour with her sister Smara in Mycenae but they do tours in/around Nafplio (where they live)
I have no connection or incentive to refer these folks just passing along the info on the guides we used and liked (although I have no frame of reference for comparison) Definitely get a private guide. Not only will you get a lot more out of the "rocks and rubble", you can get a lot of recommendations/information and have genuine conversations. In Olympia we spent the better part of an hour sitting in a shady spot in the ruins and talking about why the Greeks are/were so pissed about Macedonia Vs North Macedonia ... yeah just the name of another country will get you hot takes in Greece. Spoiler... it has to do with Alexander the great.
PS anyone who goes to Olympia, be sure to notice a small glass box in the museum with a small crushed greek helmet.... There isn't a lot of fan fair about it... It's only Miltiades game worn helmet from the battle of Marathon.... after the victory, he went to Olympia and made a sacrificial offering to Zeus for the victory... and they found it. The man who saved western civilization