Yes, these are error sources. I think you listed all parts of the bandgap circuit

The general procedure to obtain the mismatch is to
1. derive the formula for your output parameter, and then
2. differentiate it for all parameters which are not constant.
3. Add the error values (for example dR/R=1%) --> to get stdev for every error ource
4. Sum the square of the standard deviations if the error sources uncorrelated to obtain the square of the standard deviation of the whole circuit