With 5G rolling out and 1TB SD cards becoming cheap, is the 300MB format still relevant?

Yes, for these users:

No, for these users:

Recommendation: For new South blockbusters, try to get a 1GB 720p HEVC MKV file. It offers nearly double the quality while remaining download-friendly.

These files are not official. They are created by P2P (Peer-to-Peer) release groups via a specific process:

Why not 700MB or 1GB?

This refers to films from the four major South Indian film industries:

Blockbusters like KGF, RRR, Pushpa, Leo, and Kantara are highly sought after. The "South" label is used by North Indian audiences and international viewers to distinguish these from Bollywood.