Summary: In the phrase
Note how on the word panay, at the bottom left corner, there is both a kametz and a patach. Also, there is both a revii over the word and a silluq under the word.
Note how on the word tirtzach, there is both a tipcha and a silluq, and how
the tav is both a sav and a tav, a plosive and a fricative. Also, it has the same feature as above, that under the tzadi are both a patach and a kametz.
On the word panay, in his masoretic work Or Torah, Menachem de Lunzano writes the following story:
That is, a group of chachamim were discussing Torah, and they discussed the patach in panay. Someone suggested that the patach and kamatz were the result of a masoretic dispute between Ben Asher and Ben Naftali. He rejects this, and makes the question momentarily more difficult by asking why there is both a revia and a silluq on the word.
Rather, the answer is that there are two sets of trup on the aseret hadibrot. One is the taam tachton and the other the taam elyon. Here is taam tachton, as it is read privately. And here is taam elyon (although this looks to me like there are errors in it), as it is read betzibbur. In the taam tachton, there are pasuk separators just about where you would expect them. But in taam elyon, as is read in public, each Commandment is separated into a separate entity, which sometimes means that many pesukim become one, and sometimes means that one pasuk becomes many.
In the taam elyon, we would not end at the word panay, and so we would not have a silluq there. Rather, we would have a revia, and the pasuk would continue. Where there is silluq or etnachta, the word assumes pausal form, and the patach turns into a kametz. And that is the reason for the variation.
The same goes for the kametz and patach on lo tirtzach. And the dagesh vs. raphe is also a function of the trup. Since the preceding word ends in a vowel, if the trup on that preceding word is a conjunctive trup, a mesharet, then the tav would be raphei, a sav. If the trup on that preceding word is a disjunctive trup, a melech, then the tav would have a dagesh qal, and be a tav.
The Gra makes a derasha on this kametz / patach alternation in lo tirtzach. In Kol Eliyahu: