A question

Most of the episodes were based on actual Holmes stories, but they had to adapt them to modern times, and they did add extraneous storylines. Sorry I took so long to answer. I'm a slow reader.

Moonglum9 is quite correct. But to elaborate:

"A Study in Pink" is based on Sir Arthur Conan Doyle's A Study in Scarlet, but Moffat and Gatiss (AKA "Moftiss") took numerous liberties (e.g., they borrowed the cell-phone deduction from the pocket-watch deduction in ACD's The Sign of the Four), but it's one of the more true-to-ACD episodes.

They claim that "The Blind Banker" is loosely based on "The Dancing Men," and there are indeed some similarities: a brother and sister who have moved to England from another country, someone from their past who has followed them, and a secret code. But there's also quite a lot of Sign of the Four in it; for example, in both TBB and TSot4, Thief #1 has stolen a nearly priceless Asian treasure, which is then stolen from Thief #1 by Thief #2, who smuggles it into England. Thief #1 follows Thief #2, bringing along a Small Acrobatic Man who is instructed to gain entrance to the home of Thief #2 so that Thief #1 can interrogate him. However, after entering the home through a skylight, the Small Acrobatic Man kills Thief #2. Meanwhile, Doctor Watson meets a sweet, very observant blond woman who gains his affections.