Yes... Smart TVs mein lag k issues aa saktay Hain. Classical, non-smart TVs (LEDs, etc.) mein I guess, lags k issues nai aatay.
It also depends on the hardware and Internet connection speed.
Well... I personally do not like Smart TVs.
Agar aapnay FB ya YouTube TV p use karni Hai, I think then Laptops, Desktops, etc. Are intended for such use and they serve the purpose equally and efficiently well.
Even latest LEDs nowadays fully support USBs, HDMI and other medai, etc.