The Playground opens on three preset packs — quick starting points that preselect a handful of models suited to a kind of task, rather than making you pick from scratch every time.
Picking models by hand
⌘+M (or the button next to "New Chat") opens the full list instead — up to five models at once, from any provider, mixed freely.
Simulated responses
Sending a message answers once per selected model, side by side. Right now, every one of those answers is simulated — the Playground says so plainly in the response itself, not something this article is inferring.
Note. A conversation still saves to the sidebar under "Recently" and can be reopened — that part works normally. It's specifically the model replies that are placeholders for now.