Easily 100mbs would handle it. 100mbs could handle 4 Ultra HD streams plus other stuff without buffering np problem.
Standard def streams you need 2-3mbs for a clean stream. HD probably closer to 5mb. Ultra HD 4k stuff probably 10mbs could do it, but 15 to be safe. That said, bandwidth is something you shouldn't skimp on. If you can get a 100mb connection, do it.
Now, if they offer upgrades to 200+. You don't need that. If they give you 150+ for the same price as 100mb. Just take it.
I have 150mb and we can have 3 4k streams going while watching Youtube and other stuff and the only time I see buffering is why my cable company has an issue or the streaming company.