Munro Live took both connectors apart and did an overview: https://www.youtube.com/watch?v=gmjofPpThWU
Nothing stops CCS from using smaller cables. Tesla tends to have cables which aren't rated for as long of lives with the plans on replacing them more often. Most CCS dispenser manufacturers chose beefier cables which were supposedly rated for longer lives, but environmental factors and people (ab)using the cables seems to lead to those cables not having anywhere near their rated lives.
I've seen some 50kW CCS chargers with downright flimsy cables, much smaller and thinner than most Tesla cables.
CCS1 chargers can (and often do) use liquid cooling. They can also support not liquid cooling the cables as well.
Unless all these other manufacturers move their charging ports around in addition to switching connectors, the short cables on all the v3 Supercharger infrastructure is going to be an issue here for a while. If your port is in the wrong spot there's no way to reach without blocking two spaces.