INTJ and INTP are the two types most likely to be confused by the people who have them. Both are private, analytical, and impatient with small talk. The letter that differs is J versus P, and it decides what you do with an idea once you have it: build the plan, or keep pulling the idea apart.
INTJ needs the answer to become a decision; INTP needs the answer to be correct, and the decision can wait.
The only letter that differs is J versus P.
Most INTJ-or-INTP people are firmly I, N, and T and close to the middle on J/P. Work usually pushes that axis toward J, because deadlines and other people force closure; learning alone lets it drift back to P. If you test as INTJ during a busy quarter and INTP on holiday, both results were honest; they were measuring different weeks.
Your letters can come out either way if your J/P score is near the middle, and for these two types it often is. Look at the score rather than the letter, and at which situations push you toward closure.
Yes. Architect is the nickname used for INTJ and Logician for INTP on several popular tests.
Not quite. The difference is less about tidiness than about what an idea is for: INTJ wants it to produce a decision; INTP wants it to be true. Both can be organized or messy in daily life.
The four-scenario test scores each area of your life on its own, so instead of one label you see where INTJ shows up, where INTP does, and which letter is doing the moving.