Donington is open yes, much like the Red Bull Ring the first couple years it was reopened the facilities aren't even on par with what it used to have let alone more modern standards.
The GP section at Brands Hatch is much narrower than even the esses at Road Atlanta, it's barely more than 3 cars wide.
While it's hard to pass in the esses and the final turn the rest of Road Atlanta is pretty easy for traffic. At Brands there's like 3 straight turns equivalent to the last turn at Road Atlanta and Laguna Seca tier straights.