WD Green 240 GB over provisioning needed? Forrest and trees

I have bought a WD Green 240 GB SSD. I have a question about overprovisioning.

On the web there are several opinions about overprovisioning. Some say SSD manufacturers reserve space for overprovisioning and claim it is not needed to leave a certain amount of unallocated space on the driver. Others say you need to allocate it yourself.

How does this apply to WD Green 240GB or WD SSD drives in general?

Is overprovisioning generally (still) needed? It is said to be a thing of early days of SSD and that TRIM and garbage collection make it no longer necessary yet I see in a review of AnAndTech in 2016 that SSD drives are relying on overprovisioning.

Could anybody provide an authoritative breakdown of the forest and the trees of the above?