Why not go with a constant quality setting in the encoder instead of bitrate and filesize limitations?.

Thats what I do I feel CQ of 18 is indistiguishable from the original.

Bonus TIP when transcoding for static Use like storing and filesize reduction. always use a CPU never a GPU if you are after smallest filesize.

SSD is not archival storage. The NAND needs Power or it will lose its charge over time. Maybe not in one to 2 Years but maybe in 5-10.

If its active yes hdds are still cheaper unless you need less then 10tb