I would disagree with calling “gamer” laptops “cr@p” as if you look for specific use case and etc as well as the budget requirement from the OP a GOOD quality gaming laptop would run circles around the Dell Latitude/Precision or Lenovo Thinkpad’s EASILY for a fraction of the cost. Factor in the OP also possibly wants to do 1080p video editing which the “business/commercial grade” Dell’s or Lenovo within the budget would fail horribly at as they are generally meant for productivity tasks.
“Gaming” classified have come along way in terms of value and build quality for the price of the product, but to just label them crap is fairly ignorant.
As for BIOS updates sure but most of the recent vulnerabilities are hardware based and most of the patches to fix it are via the OS not the bios…. Though unless you are a high profile target or work for some fortune 500 company you wouldn’t be targeted.
For used laptops ? I would stay CLEAR as price to performance wouldn’t be worth it as used laptops are generally a generation or a few behind while limited to roughly sub 14 inch screens and for the price of an “business class / commercial grade laptop” you can get a mid to mid-high tier gaming laptop for sub $700 with a 9th gen intel i5 with a solid “DEDICATED” GPU that’s actually capable of video editing.