Deleting from Tray or Library?

So I'm still kind of new to the sims and I have a question about the tray folders and my library. 

I have all my tray and save files backed up on another drive, so I'm set with that. I'm trying to declutter quite a bit in my library and get things organized.

Loads of lots were saved to my library when I was working on builds in the beginning of my sims journey because I got saving in build mode confused with saving a lot to my library. For example I'd have 15 of the same lots saved in my library because I thought I'd lose my progress otherwise. 

So my question is, can I delete stuff from my library directly in game, and will it automatically delete them from my tray files?

Or will I have to go into my tray files directly delete whatever files I don't want? I've learned a lot within the year so I know there are multiple files attached to households, rooms, lots. And I have everything backed up so I'm not worried about losing anything. 

I play on a macbook air and I'm constantly backing up my files to an external drive about once a month, so this will also help me with storage space on my laptop. I haven't deleted anything from my tray files since I started playing so I'd love to declutter any multiple saved households, lots. 

I just want to know if deleting from the library will delete it from the trays as well. Thanks!