Is online Pind Daan in Gaya as valid as performing it in person?

Yes, within the framework of the Dharmashastra principle of niyukta karma (delegated ritual action). The Sankalp binds the merit to the person named, not the person present. A qualified pandit performing the complete Gaya ritual on your behalf, with a proper Sankalp in your name and gotra, constitutes a valid Pind Daan. Physical presence carries additional personal significance, but the ritual merit is transferred through the Sankalp regardless. Prayag Pandits’ pandits are experienced and qualified — the ritual quality is identical whether you are present or watching via live video.