If the opamp is designed as buffers for Reference voltage, then speed requirement or slew rate is not important. You may design 1st stage and 2nd stage will minimum possible current, eg 5uA to 10uA, as long as it is >> 100 time of the process leakage current.
If the opamp inputs are AC, then you need to consider slew rate. Increase current until you meet slew rate requirement.
To drive a big cap load, normally you have to add additional buffer stage after the 2nd gain stage. Withough buffer stage, the cap load will affect opamp frequency response. Yet, the 1st and 2nd stage current is still depends on slew rate, increase the current at buffer stage only if you need to provide drive capability.
Hope this helps.