Is heaven a meritocracy? That is, do the declared saints occupy a higher, happier place in heaven? If everyone is equally happy, how can extra works of charity, extra praying, and extra receiving of sacraments in this life do us any good? Or is it that the more souls there are in heaven, the happier it is, so the extra works of are not done in vain but make everyone in heaven more (but still equally) happy?
Souls will not be equal in beatitude in heaven, though whether one is a declared saint does not of itself make one more blessed in heaven. Neither does the number of other souls in heaven. Being declared a saint or sharing heaven with other souls might give souls more natural happiness, but they would only increase a soul’s beatitude—supernatural happiness—in that the soul recognizes them as things that please God.
The source of beatitude in heaven is God. Frequenting the sacraments and performing acts of charity lead to greater sanctifying grace, which leads to greater capacity to receive God’s beatitude, which leads to greater supernatural happiness in heaven.
Incidentally, the point you make about doing extra good was made in the fourth century by Jerome, who wrote:
It is our task, according to our different virtues, to prepare for ourselves different rewards. . . . If we were all going to be equal in heaven it would be useless for us to humble ourselves here in order to have a greater place there. . . . Why should virgins persevere? Why should widows toil? Why should married women be content? Let us all sin, and after we repent we shall be the same as the apostles are! (Against Jovinian 2:32 [A.D. 393])