This formation is called 6-2 because all 6 players can be hitters and 2 setters are used.
The 6-2 formation is best if your team does not have 1 strong setter.
The setter can set from position 2 (front right) or position 3 (front middle).
There is a more in-depth explanation, including serve-receive, transition and offence positions in the playlist at: https://youtube.com/playlist?list=PLqVSs3uVFUMmXKBwbyUNEGNivnnmdovQ3&si=123D4ZAXqeXQCioz
This formation is called 5-1 because 5 of the players are classified as hitters, and 1 main setter is used with an opposite.
The 5-1 formation is best if your team has a strong setter and at least 1 hitter who is capable of attack from the back row.
There is a more in-depth explanation in the playlist at: https://youtube.com/playlist?list=PLXxdrKzL9PQQgMKnU1qjnbMgjrU-kpNXD&si=mKVNyFBq9GchaVKP