That hardline setup is a coolant return back to pump/rad for the heater core, IACV, TB etc, not a feed for the head.
The water pump pushes coolant through the block & head internally before it returns through a few different paths back to the radiator. One route is using the hardline.
So long as the main hardline return is used to return coolant from the head/heater core back to the rad, then all the auxiliary stuff like TB, IACV, Oil Cooler etc are in my opinion optional. From my own experience I have not noted any major difference in cooling performance regardless if I'm driving on the road, on the track or on a eurotrip doing 9 hour drives.
I couldn't tell you what the difference would be in a few mm diameter difference between a GE & GTE hardline, but I don't think the GE causes any bottleneck. But if it makes you sleep better at night then just use a modified GTE hardline, it will work fine.