"Cheap" and "video editing at 4K" are at opposite poles.
If you have less than $1,700-2,000 to spend, buy a desktop system (NOT an all-in-one), where you can get hardware that's up to the tasks you want to perform. You're not going to find the hardware in an inexpensive notebook.
The "rule of two" remains. For the $1,000 you spend on a desktop, you'll spend $2,000 for the equivalent hardware in a notebook.