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If your load is 2A, then I guess you want a transformer rated for 2A.
The bridge rectifier should be at least twice that amperage, for reasons (1) to allow a cushion at startup when current surges, and (2) it's generally a wise approach in design.
The smoothing capacitor supplies power during gaps between supply peaks. The ripple is the amount the volt level drops between peaks. The capacitor value will be small or large, depending on how much ripple your load can tolerate. The calculations are based on the RC time constant.