Toyota Super Long Life Coolant (SLLC in short) is pre-mixed, in a ratio of 50/50. If you see the image posted by a member in this topic of the 2 liter capacity, it reads the same "50/50 Pre-mixed Anti-rust Anti-freeze" and as far as I know, the pre-mixed Toyota SLLC (pink colour) only comes in 50/50 concentration, there is no other concentration available in Toyota SLLC so I don't think there is requirement of different ratio for different Toyota engines - otherwise they would be having different types of Toyota SLLC.
Now as far as the interval for changing Toyota SLLC (again, PINK coloured one) is concerned, then according to Toyota Maintenance Guides of Europe region, the first required change mentioned for most of the engines/vehicles is:
First replace at 150,000 km (90,000 miles); after, every 90.000 km (54.000 miles)
While the first required change mentioned for Toyota Long Life Coolant (RED/GREEN coloured) is:
First replace at 60,000 km; then at 90,000 km.
After 60,000 km (36,000 miles) or 36 months, replace every 30,000 km (18,000 miles) or 24 months.
Something interesting in the maintenance manual is the fact that for the Toyota LLC (Red/Green colour), they have mentioned kilometers or 36 months, whichever comes first but for Toyota SLLC (Pink colour), NO DURATION is mentioned which makes me think changing the coolant is only needed if the kilometers are met.
I have inquired prices of Toyota SLLC (again and again, PINK colour) locally here with Ejaz Autos in Rawalpindi Saddar, it is 1950/- Rupees for 4 liters.
I don't know about driving conditions in comparison to Pakistan but for those interested, the countries under Toyota EU region are: