Linearity is good, and teflon tape is good if you so choose. it is by no means necessary for operation though. The way you're thinking of setting it up, outside for primary leak test is not necessary either, a good 5-10 psi of pressure will be enough to stop them from leaks. Make sure the supplied O-rings are in place on the barbs. As far as external radiator set up, that is how mine was initially done, then I moved it inside the case, as I found I had the necessary room after all. Do not eliminate the back exhaust case fan, you'll have a positive case pressure if you do that, and you wont have the normal flow of air either. No matter how you set up the loop, the temperature will acclimate itself the same as any other way you set up the loop. Dont worry about that IMO. Also, having the radiator outside the case does help it cool faster, as you're running cooler air through the radiator thereby lowering the temperature of the water faster than if it was inside the case.