/usr/bin/grub-mkconfig: line 270: /boot/grub/grub.cfg.new: No such file or directory

I was wondering if it was like all the kernel/systemd/etc messages or just a line or two line “Boot Cachyos..”

But it sounds like it may be the former.

So a few things .. if you want plymouth then you can follow the reverse of the following guide (make sure the packages are installed, that the hooks are included, etc);

On the other hand if you dont want the boot splash animation and you want things as silent as possible then you could follow: