Just have 1 [size] version of an image. It's easy to overcomplicate stuff in Lightroom.
For me....
Everything that's finished (processed & keyworded) gets a green label. If I'm making different edits of the same image (e.g. a B&W version and a colour version) I use virtual copies.
If I need a copy of an image for a purpose, I use the Export function. Within that, I have templates for 100, 1000, 2000 pixels & "full size" sizes so I can just export the same image in multiple different formats. If (for example) I'm posting an image here, I export at 1000px to my desktop, upload to here, then delete the image on the desktop. If I'm exporting a bunch of images for a zine or book, I do a full size export. I then delete the exports when the job is done.
As for finding images, I keyword everything with the type of photography (street, landscape, portrait etc), a person's name (if it's got family/friends in it) and then 3 words that describe the image. Occasionally I add project keywords (if I took the photo for a project for example) and camera make & film stock to allow finding/filtering on those too.
I have smart collections that automatically group based on keywords so I can find groups of images (for books or projects) easily also.
Using keywords to find images means that for me, the folder structure is largely irrelevant. Although all my photos go in subfolders under the current year as a "root" folder.