just use your onboard video card
If the PC has an onboard GPU, that is indeed the most sensible option, as those are usually good enough for desktop use. Obviously you can't game while you mine. Might be annoying to switch cables all the time though if you decide to do something GPU intensive for which the internal GPU does not suffice.
However, since OP uses a laptop, the point is most likely irrelevant since it probably only has one GPU. Laptops with two GPUs exist so OP might be lucky.
Just tried out using -mi commandline to change the intensity to 8, default was 12, the problem does seem getting much better now, I will try 7 or 6, and it does seem to affect hashrate a lot either. Thanks!!
Lowering intensity indeed does affect hashrate by a lot, one needs to find a good compromise.
May I ask what GPU your laptop has? 8+GB of VRAM sounds beefy. 
6900 XT, oof.
And if you have an Intel CPU you might also have an internal Intel GPU.