I have had a few projects manufactured as well. But that was back when Eagle was the best option (Kicad wasnt as usable or stable back in 2008-9).
I’ve really enjoyed the Code simulators in Fritzing, Tinkercad (the electronics section) and there’s a Mac/iOS app called iCircuit that offers SPICE simulating with Arduino code too and makes schematic design pretty fun for beginners. Also it links to wikipedia and data sheets for all its components. The problem is it’s not extensible, so you only get what it has included.