Guidance on using Keywords and Categories in Platinum SEO

I am looking for guidance on the use of keyword and categories in Platinum SEO.

My instinct is to apply as many keywords as are relevant to each post but I have seen suggestions that less is more, and that overdoing keywords can actually result in lower ranking on search engines.

I can’t seem to find any definitive guide to this topic. Is there such a thing? Or can you advise me what to do based on your experience please.

The use case is help pages for a photo management software product couple to a NAS based web publishing service for a target audience of prosumer photographers. So while it’s a bit technical it is not deeply technical. It’s a bit niche.

Thanks for listening

– Paul