Labelling documents to make them easier to retrieve when searching in SharePoint

I'm a bid writer for a construction company and my my memory isn't what it was. I often need to retrieve answers I've previously written and even with the excellent search functionality of SharePoint, it can take me some time to find exactly what I'm looking for. 

I've been researching different methods of 'tagging' documents and am unsure of the best way forward, and don't want to go down the wrong track. 

The tagging method in the following video looks perfect BUT it mentions that tags would only show up for me, and I have a junior bid writer who would need to use it too: https://sharepointmaven.com/a-new-way-to-tag-content-within-microsoft-365/

The Task Store option may therefore be the best solution, but it looks far more complicated than I need, and may be overkill. 

I've also seen Microsoft Syntax mentioned but not sure what it actually does. 

Each document I produce would probably have around 5 tags - client name, type of project (e.g. school),  and a few on the subject matter of the response - e.g. health and safety, environment, project team. 

Can you please advise which of the above options would be most suitable for me, or is it another solution entirely? 

Thanks in advance.