Without connecting my TV to the Internet for firmware upgrades, I would be missing out on several fixes and improvements especially with handling of higher frame rates, VRR and IIRC at least one in the HDMI ARC subsystem that was causing audio drops.
Interesting! I haven’t connected my smart LG to the net since it was new, and it handles everything I throw at it.
I prefer to use an external box as opposed to the built-in apps, to have a more responsive interface, to keep the TV as clean as possible, and to have control over choosing to update the TV or not.
I imagine all of them. This is all controlled in soft/firmware and as such is bound to have bugs. There's also updates that make better use of the hardware.