-Nineteen and Twenty were originally written as the two Androids about whom Trunks said he could barely fight them evenly one on one. I don't think that power was ever retconned, since AT wrote their battles with that in mind.
-It is stated that SSJ Vegeta doesn't start out at full power against Eighteen. It is safe to say that he didn't start out at full power against Nineteen either.
-Vegeta expected the new androids to be a lot stronger than Nineteen, yet he was still confident that he could take them out even if they attacked him all together.
Therefore, we have:
SSJ Trunks (debut) =< Nineteen << Expected Eighteen << SSJ Vegeta (warming up) ~ Eighteen (warming up) << Eighteen (more serious) ~ SSJ Vegeta (full power) << Eighteen (full power)
Is that a good starting point?
-It is stated that SSJ Vegeta doesn't start out at full power against Eighteen. It is safe to say that he didn't start out at full power against Nineteen either.
-Vegeta expected the new androids to be a lot stronger than Nineteen, yet he was still confident that he could take them out even if they attacked him all together.
Therefore, we have:
SSJ Trunks (debut) =< Nineteen << Expected Eighteen << SSJ Vegeta (warming up) ~ Eighteen (warming up) << Eighteen (more serious) ~ SSJ Vegeta (full power) << Eighteen (full power)
Is that a good starting point?