Is there an energy saving with ssd, not having a disc spinning all the time
yes, but given a HDD uses sod all energy anyway, it’s not much. You might see a little tiny benefit if running on battery.
FWIW I’m a big fan of hybrid drives. LArge capacity and cheap. They are fast for boot as the most commonly used files are automatically stored on the SSD portion. Once you’re using a prog such as Lightroom then SSD drive vs. tradtional doesn’t make much difference to editing speed, as the image is loaded into RAM for editing. Only makes a difference on export, and as I tend to just leave that to it and go and do other stuff, saving 25% of time on export isn’t worth much to me.