Trident II can carry 8 - 12 W 88 (350 KG) or W 76 (170 KG) war heads. Meaning Trident has a throw-weight around 2 tonnes at a range of 12000 KM. If India goes for a similar design then with a throw weight of 3.2 tonne they can accommodate 4 warheads (800 KG weight with a yield of 200 KT) with an effective range of 5000 KM or so.
Will be fine for a submarine, given India only wants to target Beijing from Bay of Bangal. With this India can target Beijing, Taijin, Shanghai, Chengdu, Hunan, Chongqing, Gangzhaou. With 4-5 SSBN, India can have a very effective detterance against China.
Also, India can deploy another sub group in Arabian Sea with missiles having 3 warheads each but range of 7500 KM or so and can target all of those Chinese cities from Arabian sea.