Is there a reason to use the Books app for pdf files?

Hi, I’m not talking about books that I might buy but mainly pdf files that I’ve collected. Things like manuals, operating instructions and assembly instructions.

I currently have these documents neatly filed and synchronised on iCloud Drive and read them using the built in iOS and macOS tools.

Is there a real reason to do anything different, is there something I am missing out on by not opening them in Books?

Also, if I open them in Books, are they copied into Books so I might choose to delete the file from the iCloud Drive to avoid having duplicates, or is Books just referencing, linking to the original?

Thank you for your help.