Quasi-two dimensional electronic system of organic BETS compounds is studied theoretically on the basis of mean-field calculation for the Coulomb interaction, U, together with the investigation of the effect of spin-spin interaction, J, between BETS and high Fe spin on anions. New classification on two different types of molecular arrangement, λ- and K-type, is introduced through a single parameter of band overlap, where the former with a smaller band overlap shows a Mott-like insulating state, while the latter favors a nobel spin density wave(SDW)-like state. In both states, the spin amplitude is increased by the effect of J. The value of U on BETS sites relatively smaller than that of ET is expected to be close to the metal-insulator boundary, which makes the system's ground state nature sensitive even to the effect of small value of J as well as to the difference in the band structure, which explains the various ground states of this family within the same scheme, in accordance with the experiments.