Hair serum or prewash hair oil advice?

I have recently cut my hair short due to lots of bleach damage and breakage - I’ve had to had layers cut in to avoid the damage travelling up my hair strands, and I’m not a huge fan of it. I’ve accepted my fate, as it’s done now, but because I’ve also recently noticed thinning on the sides of my head/around my temples, I’ve started looking into hair serums or pre wash oils to help promote healthy/thicker hair growth.

Some of the ones I’m considering are:

The hairsyrup growsmary oil The UK Lash hair serum The Coco&Eve hair serum Hair+Me capsules

Does anyone have any experience using these/any other recs?

Thank you!