Did the human-type Cylons exist in the original BSG series from decades ago?

Are you talking about the original series from the late 70s or the "original" BSG 2003 miniseries?

If the late 70s program, no. The "human" cylons weren't part of the mythology. The Cylons in that series were these lizard creatures (remember "Imperious Leader") who were almost extinct and who used the robot "Centurians" to carry out their battle plans.

If you are talkinga bout the 2003 miniseries. They did establish the humanoid cylons from the get go when the Six meets up with the human emissary after 40 years of radio silence between both "races".

Hope that helps.

In the original series, no. However, there was a so-called continuation series, "Galactica 1980", an episode of which was called " The Night The Cylons Landed" which featured two humanoid Cylon models. So, it depends on whether you count that poorly regarded series as part of the cannon of BSG or not. Most fans don't. If the original series had continued with a genuine second season, however.. script outlines for unaired episodes were supposed to contain human models

there were many aliens and planets on the original series of bsg but no humanoid cylons... tho some aliens were actually working for the cylons