Did you got an answer from ASUS ? I really like this laptop and i´m still trying to fix the issue before returning it. Btw i mailed them too, even attached a video of the fps drops, they said they were going to analyze and try to replicate the issue.
Got the laptop from amazon too, the same problems, so far installing AMD 19.12.1 drivers made it a bit better, if I can’t find a fix soon I will just ask for a refund. Sucks because I really like this laptop.