CoW is probably a good idea whether you use fork or not. Or rather, fork is probably a better option than just exec exactly because it can benefit from CoW.

At least on systems with virtual addressing. If you want to go into physical addressing, then yes, maybe it's a problem. But Linux will never touch anything with physical addressing, so I don't see what people are complaining about.

CoW is probably a good idea regardless, yeah. Overcommit is more questionable. Regardless, both ought to be argued based on their own merits. It's unfortunate that both are necessary as a consequence of fork().