Best approach large race track model - frustrum culling - Prefab/Parent questions.

Hello Peoples, Please correct me if I am wrong.

Before I do this wrong, maybe someone could share their knowledge.

I have created a large race track about 2 miles in distance and 50,000 polygons.
It is not modular at all.
With regard to track preparation for frustrum culling what is the best approach.:-

This track is one model at the moment similar to a terrrain in size. Does Unity render the whole object if only part is in view? I presume yes as a model not sure about terrain?

Do I split the track into say 20 pieces and mark as static so it only renders within the frustrum? I presume yes.

If I parent all the static pieces under a static dummy will it only render those within the frustrum? Help?

If I create a single prefab containing individual parts (everything marked as static) will it render only those parts within frustrum? Help?

Thanks for your help.