I plan on using Fritzing for PCBs, but will need sims like Falstag to make sure the circuit works. Is there another purpose for Fritzing other then PCB fab?
Yes, there is. Fritzing can be used to draw out breadboard and schematic circuits.
There’s also a simple simulator if you’re using Fritzing 0.9.10 or later versions. It may be disabled by default. To enable it, go to Edit → Preferences (or ⌘+, File → Preferences in macOS), select the “Beta Features” tab, and check the “enable simulator” checkbox. Fritzing will save this option, and you will only need to activate the simulator once. Of course, you can still disable it anytime in the preferences dialog.
The simulator only allows you to use parts with SPICE models. Any part without SPICE models will be greyed out when you simulate it.
I think there may be a bin with simulation parts in it. @fai (who wrote the simulator) can probably give you better advise on what is available than I can.
If the part that you want is not in Fritzing, do a Google search using the template: [part_name] fritzing, replacing [part_name] with the part you want. Do search within the forum as some search engines may not show all the results. If you still cannot find it, then request for the part you want under the parts help category.
As @gtmize mentioned, there is a basic simulator in Fritzing (but will not simulate Arduinos). Check the current capabilities here: https://blog.fritzing.org/2022/06/27/Simulating-Circuits-with-Fritzing
In addition, you can also simulate transitory analysis since Fritzing 1.04. It is still a beta feature but it is functional. To use it, you must launch Fritzing in debug mode (using the terminal and adding the argument “-d”) and select the transitory mode in the simulation button. Please, notice, that there are not many parts that have spice models. See an example using a 555 and more info about the transitory analysis in this thread: Using 555 timer chip doesn't work