The Clan energy weapons generate more heat, as you're comparing ER to standard. The Sphere has access to ER energy tech, but they don't see the Clan's boost in laser damage or all of the extra range. In the end, if heat is a primary concern (which it often is in IS laser 'Mechs, though even IS Double Heat Sinks help with that problem), you'll probably want to stick with the standard lasers, which generate less heat than the ER versions.
We don't know yet. I would assume something similar to the latter.