BSUN K1 linear switch is a budget-friendly switch designed by QN Studio and manufactured by BSUN using their newest bottom housing and stem molds. Although the specs make them look clacky and loud, don't forget this is still BSUN. Their mold design tends to make switches sound deeper; This is also the case with K1 switches. Even with the fiberglass in the bottom housing, they don't sound very much clacky. The best word to describe their sound profile is probably "thocky".
Factory lubing-wise, QN chose to go with as little lube as possible on the stem sliders and bottom housing rails. This was done in order to avoid any potential lube pooling problem while still retaining the smoothness.
