So there are two ways to say "conversation", "samtal" and "konversation" right?
Yes, that's correct.
Shouldn't "we had a nice chat" be acceptable here?
A chat is more of a "pratstund".
TTS sounds like it's beatboxing. Jag gillar det lol
Can trevlig sometimes have a different and negative meaning?
No, then it is "otrevlig" :).
Can "trevlig" also mean "lovely" as well as "nice"?
To me, "lovely" is stronger and I'd translate that to "härlig", "underbar" or maybe "förtjusande".
is "delightful" too strong of a word to be translated as "trevlig"?
Yes, trevlig is pretty bland.
Maybe it's just me, but it sounds to me like "konversation" could be one of those words that's maybe a little too rigid or formal for everyday use. Am I correct?
Not necessarily, I think. But I would probably have used "samtal" instead.
My layman-ish observation is that some young people use "konversation" due to English influence on Swedish. It sounds perfectly normal though.
Is friendly conversation not okay?
No, that's better translated as e.g. vänskaplig.