never buy lenovo, poor value and quality nowadays, same with HP.

I suggest looking at alienware, some MSI lines, ASUS, dell inspirons (if looks not important), acer predator, clevo

Many brands both major and minor to choose from. Dell pro warranty is top notch, so if you buy dell make sure you get their pro warranty included.

For CPU, i suggest you go with 8gen intel CPU, as they have cheaper quad cores and 6 cores.

Thunderbolt 3 is a must as that lets you upgrade your GPU in the future. It also lets you use the intel IGP for external displays as in 99% of nvidia optimus laptops, the dGPU is connected to the display ports.

Some laptops have switchable that lets you choose to switch the laptop screen to dGPU rather than IGP allowing you to use syncs like freesync and nvidia variant easily. But if you connect to external monitor for gaming this feature is not needed.

not particularly as many models fit what you want, so i just give you advice on what to look for.
8th gen CPU, preferably 6 core
16GB ram
SSD and HDD combo (not SSHD)
Screen - do you want 144hz? ability to use GPU sync?