Amazing cheap, non-touristy eats in Athens, Delphi, Meteora, Napflio, Mystras, Kardamyli?

Assorted thoughts on a few venues:
ATHENS - I believe u r staying in Central Athens, and hard to recommend "non-touristy" there, but a few thoughts -- many small gyro shops where u can step up to a counter & get a good gyro cheapo... look around & compare. Also, this applies many places, in the AM bakeries often have an assortment of hero-type sandwiches + tiropitas + spanakopita to go... there are fruit carts around, and Voila! picnic fare for the National Gardens. NOTE: there are 2 well-known places at a corner of Monastiraki square where you can get a big gyro platter very cheap, but be aware, very crowded & lots of little gypsy-kids with thieving fingers.

NAFPLIO/ASINE - in a thread about swims, I mentioned this little cove & its family-run taverna. One time when we swam & then decided on dinner, they suggested fresh fish. they had a little rolling steel case, like a filing cabinet filled with ice & fish. top drawer, tiny fish, @ flat price, 2nd drawer, bigger fish, etc. Then they fried them, crispy and SO Delish! at very moderate prices. (as seasoned travelers u of course are aware of the Med/Aegean over-fishing situation, resulting in high prices for large-species fish).

NAFPLIO -- the borderline between Old City & "modern" nafplio is Syngrou, runninig straaight from front of Palamidi to harbour. Near Harbor, on the "new" side is a large tree-filled park, with playgrounds & small cafes at edge, which is TOTALLY used by locals ... of an evening, full of life, children on slides, music from cafes, etc. You can find a corner kiosks with seating, buy a slice of pizza & a beer and be completely out of the tourist lane.

DELPHI - we arrived late-day, checked in Hotel Pan, asked for low-key place for eatsl... landlord pointed up the way where 2 streets meet (the "square"? Triangle?). On the downhill side was a little cafe, inside were teens playing pool, outside had nice terrace in the sunset. We had a lovely spaghetti dinner for v. little, PLUS the topper of Delphi stay ... local water! Straight from the pitcher, nectar of the gods!! We asked, what brand? Waitress said, from the faucet. She pointed up at looming Mt Parnassus & said, it comes from the snow-melt. We filled our thermoses.

As you are interested in Street food, Athens awaits you every weekend until the end of May

https://athensstreetfoodfestival.gr/en/

If you arrive too late in Athens for this festival you will find street food everywhere in town.

Alternatively, from Monastiraki Square, taking Athina Avenue north, there is the Athens Municipal Market (less than 15 minutes walk)
In the market there are small, friendly and inexpensive traditional restaurants.

Alternatively of the alternatively you can also explore the Omonia Square area (preferably during the day, avoiding the night), or further north the Exarcheia district. You will find a lot of street food places.