I don't have a 4K tv but I can see 4K options in the menu, any buffering would depend on your broadband connection and lip sync issues would depend on your set up
... and on how well the specific app is written / supported.
as an examples,
1.many people report Netflix on Amaon fire devices is buggy, because Amazon have no interest in making it work better, and because some techies say that Amazon OS starves it of needed resources.
2. my Samsung Tizen TV netflix has a couple of quirks which are not present in my Roku app. The Samsung Tv version often starts with " we are having trouble playing that... even if "that" is a menu scroll, then it recovers and works fine until the next day- that would be poor cache management- most likely , or app not cleanly closing .
Smart Tv apps run in java screpit with the TV browser, I discovered, they are no true stand lone apps, and cross corruption can easily happen.
I don't know how netflix is implemented on V6 and how well it will stay up to date. The netflix android app updates quite frequently, ans the google play store info for why usually says " bug fixes"
There are other differences: netflix on Roku as a forward skip function for bypassing opening credits, with helpful thumbnail stills. The android version has only a not very useful 30 seconds back. to go forwards it's guesswork in the seek bar
Just been on to 150 and they suggested that a high speed hdmi cable, which should have been fitted on install, was needed so swopped out and problem gone. Just add that they credited me with £10 to get the new cable which as I said it should have come with.
The installer never fitted the needed HDMI 2.0 cables?
I assumed since the Tivo came with cables so would the V6, as my mothers getting her 2 Tivos swapped over to V6's on Wed.
I can assure you no cables are going to be ran all over carpets or skirting's, the original install 15+yrs ago was all under the floor so if needed I can pull the cables back and forth with string to add more cables for the engineer.
The CS guy told me a mix and match of wrong info like the engineer brings Ethernet cables and they will need be long ones for my install and he will add this to comments and the V6 does not use WIFI but can do via Plug in adapters (power line/WIFI I assume he meant) can be used but at extra cost.
I wonder if the engineer will even turn up or and even then will it end in a ballsup like many other install here.
I will not accept out of box V6's all scratched or missing remotes or power supplies, he can leave.