Is there a tool that can simulate some types of Kicad outputs? I mean something like do a PCB design for a simple circuit and then "run" or debug it in some way.
For analog electrical simulation there's SPICE. Kicad has a spice tool built in, but I haven't used it. It has some improvements in Kicad 6. I use LTSpice.
For digital or systems simulation there's Renode. You have to recreate the system in Renode,there's no Kicad integration.
I would honestly manually recreate my simple PCB designs in Falstad's simulator[1] and use judgment to decide whether further thermal or high-freq analysis is necessary.
I haven't looked in a few years, but you'll likely be hard-pressed to find an open source simulator that will give you analog, pure digital, "real" digital (logic with slew/noise/nonlinearities), electromagnetic, and thermal simulations plus usability.
ANSYS is a well-established professional simulation suite and doesn't even really meet the usability threshold, in my opinion.
For digital or systems simulation there's Renode. You have to recreate the system in Renode,there's no Kicad integration.