The RR engine one is last one of existing order (not a sole example), but there have been problems with the RR engines, and a handful of planes are out of use awaiting engine parts,
6 are extra planes ordered later, and probably fed up with Rolls Royce poor spare parts delivery, so took decision to switch to GE engines.
Although I have described it as a British Airways order, it is strictly the parent IAG (International Airlines Group) that has ordered, and there are also 21 Airbus A330-900neo and 6 A350-900 (probably for Iberia or Aer Lingus). Sounds like the A330s will be Rolls Royce powered (dont think engines for A350-9 have been announced yet).
The 787-10 is approx same size as the 43 777-2 that BA has
787-10 (existing, maybe not new ones) are configured
First 8, Business 48, Premium Economy 35, Economy 165.
777-2 are nowadays in 3 different configurations :
First 8, Business 49, Premium Econ 40, Economy 138
no First, Business 32, Prem 52, Econ 252
no First, Business 48, Prem 40, Economy 184