different combine on different texture units

Since there is NV_texture_env_combine4,
ATI_texture_env_combine3
and
ARB_texture_env_combine

Can I activate one type on a specific texture unit, and another on another texture unit?

It appears that the NV version has gone a different road and the ATI and ARB have more in common.

What if I use ARB_dot3 on a certain tex unit and NV on another?

I hope someone can answer by tommorow.