In our standard practice , for big size line we follow option 2 as you mention.
Let us consider 10, 20 30 are node point of header , where 20 is the tee point.
For Branch 20 to 200 is rigid & 200 to 210 branch pipe.
We first check default Caesar SIF for header & branch from Environment-Review SIF at intersection node.
We then manually put SIF value as follow
Node 10 to 20 , put SIF at 20 ( Caesar default header stiffness)
Node 20 to 30 , put SIF at 20 ( Caesar default header stiffness)
Node 200 to 210 , put SIF at 200 ( Caesar default branch stiffness, since here branch is 45 degree we multiply default value with 1.5).