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I do not have enough information about your framing to comment on that. Generally speaking, this assignment, in most cases, has a limited effect on elements of Vertical Lateral load resisting system. When Structural Engineers intend to check forces in chord members of diaphragm, for the purpose of estimating its suitability to transfer lateral forces to vertical elements, they use this semi-rigid option. The rigid-option does not let you check these diaphragm forces. The assignment also depends on your structural system. CSi has a simple video on it. You cannot assign membrane behavior to column. You can assign membrane behavior to shear walls. It is reasonable simplification for a majority of design scenarios.

Salam, You can make an envelope for load combinations, and check the forces corresponding to the enveloped combination. in this way you will be able to check against the governing load combination. hope it helps!