Sicilian Pawn Structure Nxc6 bxc6

But I don't know how to exploit it best as black. Should black be playing g6, e6, e5, d5, Be6, Ba6, Qa5, or what? What are the best middlegame plans and what are some factors for how you choose between them? I would think ...d5 would be the strongest plan but often it needs preparation because white can push past with e5 or clamp on c5. I don't know whether my dark-squared bishop should go on g7 or somewhere else.

Here's some examples of some of my games (some blitz, classical, correspondence etc) where they captured on c6. What am I doing fundamentally right or wrong?

I've faced similar positions often too and used the 2 setups you mention plus a quick d5 when a bishop is exposed on c4. I dont have a definitive opinion as for which to take--it depends on how mobile black's center pawns will be in each case.  -Bill

So simply ...e5__Be7__O-O__d5 and then is a game where black has control of the center.

Afterwards if you play against ai.Hiarcs with black probably you will lose because chess is complicated etc. but at the end of opening it is satisfactory for black I find.

I found about 25 master games. In those white mostly plays Bd3, f4, Qe1-h4 etc. Black responds best to this setup with g6, Bg7, Rb1, N-d7-c5 and at the right time d5 and Nxd3. That's what I found in my database.

As black I won at least 60%. I usually play g6 and Bg7.i can't find the games as they are deep in archives. I played both a5 and Rb8. Both works.