Here is the wall

No one knows what you want to set on the shelves.... use masking tape to test what you like..as to placement. I'd start with one below the outlet so I could place something in front of it and eliminate the side table. Meaning you might like three and test first. Notch the shelf for the cord

I have purchased a variety of picture frames from 14inches to 8x11 to 5x7, and some small vases and figurines. I want it to look modern and elegant but not too cluttered. I have small faux hanging plants I can experiment with also.

Already sounds a bit boho and cluttered ? Depends what YOU want. Not us.

Modern and elegant is not cramming a whole mess of stuff on some shelves .And fake plants are never good anywhere anytime.

How deep are the picture ledges and how wide is the walkway between the sofa arm edge and the wall on which you want to mount the ledges? It would be easy to bump the ledge or hit your head on a ledge corner if it’s a tight squeeze.

One large piece of artwok. Keep it simple.

The ledge is 3.7 inches deep, and the table between the wall and sofa is 12 inches. I like the table there to get some distance from the wall and to have a place to put things. I have a boho theme in the living room. I like the tip to not put too much on them, especially if I use 3.

Any feedback on whether I should center or stagger them? The wall is 60 inches and the ledges are 36 inches.

I would center them for a simpler look

Use a few pieces of TAPE and decide what you like