CNC lists 1.006.245.120 EOS as Total Supply and
906.245.118 EOS as Circulating Supply so your rough 1billion are probably valid for Total Supply
Block.one's account with accountname "b1" holds 10% of the initial token-supply but these tokens are locked for 10 years. That's why CMC only shows 900Mil instead of 1Billion.
For the Total Supply I wouldn't remove any additional accounts from the snapshot.
For Circulating Supply I would also remove "eosio.ramfee", "eosio.saving" as these balances are (currently) fully locked, as long as REX is not enabled - and the "b1"-account.
I would assume that CMC is not removing these system-accounts from their calculations so the answer to your question depends on what exactly you want to calculate.