Interesting frame.
The L section corner posts are standard features here for houses built in that era - 1820s to 1860. Most are 12x12 but I have seen 8x8 on some single story houses.
I have seen T section posts at interior bents.
These frames are hard to study as they are almost all behind plaster or paneling.
Braces here are usually down braces - mostly on a 45° but I have seen them steeper.
I've never seen centered timbers here. Plain old quick and dirty square rule is the usual.