If anyone hear could vouch for Qucs simulator and explain a bit why it's good I would love to add it. It was recommended before but without reasoning and I haven't had a chance to try it.
Qucs is trying to emulate Keysight's ADS software. It is mainly RF focused, but can do a lot more. ADS is awesome. Qucs has great potential, but needs some work. It is still useful, though.