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.