Updates: Prior to my another track day coming up, I took my car to another inspection, especially focused at front suspension.
Surprisingly, the mechanics found that the bolts for the upper control a-arms are slightly loosened. Although without a torque wrench, the mechanics were able to tighten the bolts a bit more with a short wrench by hand measure (I guess could be around approximate 50 lbs). I didn't look into the service manual, but to my little knowledge, these bolts should be torqued some where over 50lbs.
The front suspension upper control a-arms are now tightened (by hand measure). After the repair, the rattle was disappeared at first, but after 30 mins testing, it still appears at low speed (30 km/hr) with clutch in or out, and the noise is especially profound at 2-3rpm; however, the noise is significantly lowered. I will keep on finding if any bolts are loosened and later try the "disc brake quiet".