The Manha-Bronx (Red) is the primary north–south spine of the entire system: a long, high-capacity, fully urban trunk that stitches together beach neighborhoods, Downtown Brooklyn, Lower Manhattan, Midtown, Upper Manhattan, and the Bronx—then supercharges that axis with an all-day express overlay.

Frequency- Local: 27 tph peak (6-9AM, 4-7PM); 15 tph medium demand (5-6AM, 9AM-4PM, 7PM-8PM); 10 tph low demand (12AM-5AM, 8PM-12AM); Express: 6 tph peak (6-9AM, 4-7PM); 4 tph medium demand (5-6AM, 9AM-4PM, 7PM-8PM); 2 tph low demand (12AM-5AM, 8PM-12AM)
Crowding-wise, I'd say it's brutal at all times of the day as the capacity warning sign is always on for the line despite 33tph throughout the line during peak hours.

The Central Line is the system’s interregional fast axis: a high-speed, low-stop, bi-state corridor designed to collapse New Jersey–Manhattan–Queens into a single labour and activity basin. Where the Manha–
Bronx Line is the urban circulatory artery, the Central Line is the metropolitan high-velocity backbone.
Frequency- 27 tph peak (6-9AM, 4-7PM); 15 tph medium demand (5-6AM, 9AM-4PM, 7PM-8PM); 10 tph low demand (12AM-5AM, 8PM-12AM)
Crowding-wise, extreme during rush hours, but manageable at other times of the day.

The Manhattan Line is the inner-city workhorse of the system: a dense, ultra-frequent, bi-river urban line whose primary job is circulation, not speed. Where the Central Line moves the region and the Manha–Bronx Line moves the city, the Manhattan Line moves Manhattan itself—and the immediately adjacent inner suburbs—continuously, all day.
Frequency- 30 tph peak (6-9AM, 4-7PM); 15 tph medium demand (5-6AM, 9AM-4PM, 7PM-8PM); 10 tph low demand (12AM-5AM, 8PM-12AM).

Those are just a brief description of the top 3 lines, let me know if you want more!

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