I have some components here to make an SMPS from mains for a CV/CC power supply for my workshop, and I decided to add a linear post-regulator to smooth the output. To avoid big heatsinks I wanted the SMPS voltage to follow the post-regulator voltage when I adjust it, and I've found a possible solution from this question. However my simulations showed better results while using an OpAmp (image below).
As you can see, I set up the comparator of the SMPS in a way that the output voltage of the post-regulator will determine the output voltage of the SMPS (keeping it always 5V more then the post-regulator output for example, precision is not a problem). The circuit works fine on simulation, however I wanted to know if ripple, noises or imperfections of hardware that doesn't exist in my simulation might make this a bad idea, and what filters should I study to put on the output of this OpAmp (if any) to avoid any problems with this "follower" circuit before I buy the components I need.