Changing 3D solid elements to 2D plane elements results in a large reduction in node count which speeds up the solution.

Beam elements already have few nodes in the model so there is no great need to reduce the node count.

You can add a Displacement BC to all the nodes to set 3 of the DOF on each node to 0 to make it a planar problem. If the beam S-bend is in the X-Y plane, then the Z, RotX and RotY DOF can be set to 0 and the beam will bend only in the X-Y plane and the model will solve slightly faster because the number of unknowns was cut in half. The real benefit is the solution may be more stable because the pipe can't go sideways anymore, however, that may be less realisitic.