they are not JST otherwise you'd have been able to use one of the adapters AC has. Corsair uses a small Molex connector.
To adapt you could go several routes. there's no direct corsair adapters to RGBpx that i know of, but you can go Corsair to standard ARGB, then ARGB to rgbpx :
The XG7 should come with a corsair to argb adapter cable, otherwise you can get one of those :
https://piratedog.tech/collections/rgb-adapters/products/aura-mystic-light-motherboard-a-rgb-to-corsair-rgb-adapter
Then you would need something like this to connect to an octo or Next controller
https://shop.aquacomputer.de/product_info.php?products_id=3829
https://shop.aquacomputer.de/product_info.php?products_id=3764
Or if you ever consider getting a Farbwerk360, it already has standard ARGB connectors besides the RGBpx ones, so you'd only need the corsair adapter, or the piratedog tech adapter cable.
And since the XC7 daisy chains to the XG7, you only need one channel to control both.
if you want to connect to the motherboard for now, you already have everything you need if you didn't lose the XG7 adapter