Nafl prayers are voluntary prayers. If you do not pray them you are not sinful, but missing out on great benefits.
Praying behind the imam on TV is not permissible.

What are the rulings on nawafl prayers in general? I pray my regular thuhr on jumu’ah at home as I am a female. After which at the time of live telecast of the jumu’ah at Makkah I pray again following the imam on TV facing my qiblah as nafl. This is a ritual for me every Friday. Is it permissible?

Prayer | August 26, 2014 2:17 pm
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My husband was on journey and he shortened his prayer. But my brother in-law insisted on performing with jama. He said it is good to pray in jama even if we are travelers. What is your advice on this?
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I pray Fard prayer in masjid. Should I pray the sunnah prayers after the fard in masjid or go home and pray? Which one is the best? Please advice.