is there a way I can launch a chat window where I can feed everything into it - user names, emotes, memes, links, etc and just let it run + screen cap it?
You could put multiple bots in (one of your) own channel(s) and simulate a chat this way. Downside is that you would have to create as many bot accounts as you want to simulate users in the channel. Also, you could only use the emotes provided by Twitch or the streamers your bot accounts are a sub of.
It would probably be easier to simply build a simple clone of the Twitch chat; it isn’t exactly a complicated piece of HTML/CSS after all. Then you could script it anyway you want, for example having a JSON file with the chat contents you want to appear. Downside is that you would first have to create the chat clone. Upside is that you can include your custom emotes that aren’t actually uploaded to Twitch.