Another vote for Weathertech. The Tuxmat may be softer feel and look fancier, but I've always loved the ruggedness, fit, and ease of washing for Weathertech.
I have the same rattle when engine/exhaust are cold, with newly installed AWE touring and AA downpipe. Made adjustments to make sure it’s not contacting the cross brace. It doesn’t seem to be contacting heat shield but not 100% sure. A friend told me pushing the heat shield up helped his.
I used this stuff on my Tacoma when I took an 8 day trip across country. Had no rock chips and worked great. However, certain areas I didn't layer on thick enough were extremely difficult to peel off. Some of it stayed on a year or more because I didn't want to scratch the paint trying to get it...