The use of metal brackets in traditional timber-framing is not unknown.
In older frames this is much more likely to be required to repair or strengthen the frame. Later on The Victorians made good use of metal brackets in their building designs e.g. see the attached pic of the old Bradford Wool Hall where ridge brackets not unlike your no3 image have been employed. Unless dry seasoned wood is used you will doubtless get gaps opening up. Structurally these probably don't matter but might not look great.
The best answer to your query is probably to sign up to take a course in timber-framing e.g. as run by Jim Rogers (see below) or Heartwood (TFG).
