Best of luck! I did signage for a furniture place before animation and raster files can get super heavy at large scale. Hopefully you can make it work!

As I said earlier, if your printer recommends 150dpi, then potentially you could manage 20000px or so wide in PS if there wasn't a huge amount of layers and fx

In inDesign, anything you import is still linked to the original file, so you can reopen, tweak it and it will update on save. I'd do a low res mockup, get colours locked and import it as a base to add stuff on top of. The back and forth is a pain, but at least it's not 40000px in PS at 300dpi

If you can, lay it out in inDesign. Smaller raster items compiled into one large file will not melt your pc this way, and it has low detail settings for layout that let you make changes faster. Some instances you can drop the dpi below 300, but that may depend on the print company you're using