a minor quibble, ltspice/switchercad is really a general purpose spice package. they have neatly packaged many of (but not all as I found out) the LT products for easy use but I've used it quite nicely for all sorts of non-switch mode simulations.
they do have a very nice way to design smps circuits with their parts - "switch selector guide" and it will walk you through creating a power supply design that you can then play with. You just define input V, output V and output I and it does all the work.