A big photograph mess

My photos have been stored for years on my iMac, first under iPhotos and then in Photos. I've neglected to maintain them and to be honest, I've just been uploading new photos to Photos and then not really paying any attention to how I had it all set up and maintained/backed-up. I've got some old iPhoto archive sitting on dropbox, I am too scared to delete iPhoto app because of this. And I am worried that by deleting all app I might lose precious photos.

I am now in a situation where I want my photos all in one place, backed up via Time Machine and then also dropbox.

I don't love Photos as an app and to be honest I would like a less heavy way to manage them all. But I am also happy to use it if it is the right solution.

In my dream world I want an app I can download now, allow it to search my entire hard drive for photos and then reindex them all to check for duplicates. I am not sure if I am asking for the impossible.

So questions:

• what could this solution be?
• is is possible to start from scratch with Photos if this is the way to go, to ensure it has everything?

I am so terrified of losing photos and I really am just looking for a fail safe way to ensure I have got them all, and can manage them easily ongoing.

I used to work in high tech PR, be incredibly techie and had all this stuff under control. Various life circumstances mean I could now do with some guidance.

Be kind!

Thank you.