Yes...the HS goes away. But I would think twice about it, in the ICY the 980 (tested with the non-HS variant) already gets quite warm when connected to Gen3.

So I would buy without a heatsink and then connect it really well to the housing (as a heatsink). With HS in order to then remove HS is, I think, a negligible added value. A large enclosure gets warm more slowly...but the SSD in it doesn't because of this...actually you want little insulation value, that the enclosure gets as hot as possible.