The screw does not need to be held at the top as it does not provide support. The Z rods do that.

In fact, the threaded rod is better being unsupported at one end as these often do not run true. Being fixed at both ends can cause misalignment in your print due to pressure placed on the Z rods.

A threaded rod will also not make noise as it is held by the motor on one end and the threaded bush on the table assembly. Upload a video of the noise you hear.

Enclosure also need for specialty filaments like PP and PE. 2-3% shrinkage on those.