Rough calculations for heatsink and mains current
You are almost correct .The RMS current is greater than the average current because the cap input filter draws peaky lumps of current when the eltec cap is being charged .The peaks can be several times the average current .If the DC filter cap is very large which is the case when good holdup performance is needed it is the transformer source impedance that limits peak current .Small mains power transformers have a mainly resistive source impedance at mains frequencies .A rule of thumb is that the Average current is about 70 % of the RMS current so your fuse must be factored accordingly .With proper transformer information and simulation the rule of thumb can be improved on .This is for steady state but at power up the filter cap is at zero volts maximising peak charging current and the transformer itself has an inrush current .Summing up your primary fuse has to be way bigger than your power draw would imply and is only a last ditch fire protection .This is why thermal overloads are a good way to protect mains transformers.