I'm similar to Cheryl in my organization, and I've tried the spreadsheet before after seeing her awesomeness and got annoyed that I couldn't sort/filter in Excel and have the images still show up, so I abandoned that lol
For my photos I just recently decided to start using my Mac as a Mac instead of a Windows-substitute. I imported all my photos into 'Photos', one folder at a time so I could create an album for each month (how they were arranged in Windows folders). I have a 'folder' for each year, with albums for each month inside. Once a month I go through my photos and tag them, delete the bad/blurry/extras (this takes maybe 10-15 min. a month). I tag the person, event, and "To be scrapped" if I think it would be good on a page. Then I can search by event, or person, or just look in the date folder. I LOVE that this all carries over onto my phone with iCloud photo library, even the organizational structure, and I can search keywords there too. After I've done the month I export them to my EHD as an on-site backup (including keywords).
For my layouts, I save them on my EHD as YYYY-MM - Layout name ... I do this because when I get it printed the title shows up on the back, then I always know when the layout was from, even if I forgot to put a date in the journaling. Plus I print individual layouts not in books, so it helps me organize them when I get them. I have folders for each year, and I keep a web size copy in Mac Photos in the month album so I know when I'm browsing photos to scrap that hey, I've already done that one.
For Scrapbooking 'stuff' I organize by Designer folder, then by Kit Name - Designer name. I copy the preview of the kit/template into Photos (a different library than my photos library) and tag the preview with 'New to use', theme/season, Kit/Template/Element, etc, etc etc. This takes just seconds after unzipping, etc. Then I can search by 'Spring' and everything spring will come up. I can see the kit name and such on the preview, so I know where to find it in my designers folder. If it's a collab I store it in the folder for the designer's folder whose name comes first on the preview. When I've used it I delete the 'new' tag and add 'used'.
Phew - sorry, that was long winded.