126 layers inpad? OK, you are catching up to Bert Monroy and his "Making of Times Square." Though I believe he had several thousand before he was done! Maybe a million or a trillion. Billions and billions of galaxies in the famous words of Carl Sagan.
I, like you, hate to merge layers. I'm a stickler for nondestructive layers, and make tons of smart objects so I can adjust filters as well as adjustment layers. I often copy merge so I can continue further manipulation of one layer instead of 6. Then I group the original layers, name them, and move them to the very bottom (not always move them though -- sometimes very convenient to keep where they are or I only copy-merge to make a blend layer over originals) and turn them off.
It makes for a large file. But who cares. The only time that becomes a consideration for me is if it gets so big, PS slows down. I've had it crash a couple of times and had to redo a lot ow work. Sometimes the result of that is improved technique, but mostly it's a pain. I save frequently even if it is a long process of rendering and formatting. I'm paranoid now.
Another trick is to save as a new psd as a stage. You can save stages in PS as you work, but they are gone once you close the document. Making a new PS allows me to delete the not in use files, the big groups that are taking up unnecessary megabytes. Then I build on that. Always have those original layers tucked away safely. My hint for the day. Now I'm exhausted of ideas, lol!