I have TUF Dash FX516PM (RTX 3060 version) and have experienced PCIE speed issue. I tried to monitor using TechPowerUp GPU-Z tool.
What happens is whenever my laptop wakes up from sleep and I start a game, the PCIE speed has to shift from 4.0 1.1x to 4.0 4x, but after a minute or two, it drops to 4.0 1x itself. Under ideal conditions same game's (Rocket League for example) GPU load is 50-60%, whereas when it drops to 1x speed, GPU load is 95-99 %. This causes the laptop to eventually crash with a BSOD.
It took me two months and a complete board change in my laptop (under warranty since the service guy had no clue too) to figure out it is not a hardware issue, but has to do most likely with Asus' BIOS setup which is not initializing the appropriate control to NVIDIA drivers on wake from sleep state.
The laptop works fine when it boots from shutdown. This has been reported in several NVIDIA forums too from as early as 3 years back. This has been a long standing issue, and can't believe Asus hasn't fixed this yet.
I am just explaining this out here so fellow TUF Dash users find a post that talks about this. The solution to fix this is to avoid using sleep state and switch to using hibernate mode. That doesn't mess up with NVIDIA GPU drivers.
A reference post on NVIDIA forums -
https://www.nvidia.com/en-us/geforce/forums/game-ready-drivers/13/284488/bsod-after-wake-from-sleep/