The procedure for an 18th century marriage in Scotland was this. First the couple went to the session clerk of the parish and announced that they intended to marry ("contracted for marriage"). This was then recorded. At the same time, they each paid a sum of money (called "pledges") to show their seriousness. Sometimes the name of a "cautioner" who would stand good for the money was given instead. The banns were then read out in church three successive times. Occasionally this was done twice in a day if the service was split into a morning and afternoon session. If there were no objections, the marriage then took place. It was normally held at the bride's parents' home.
A short time after the wedding, the couple could then apply to have the pledges returned to them. If there was no scandal attached to the marriage, this would then be done. However, if the wedding did not take place within forty days of the "booking" (the initial statement to the clerk that they intended to marry), if there was drunkenness, inappropriate dancing or the like at the wedding celebration, or if it was rapidly discovered that the bride was already pregnant, then the pledges were forfeit and went into the poor box.
Where the bride and groom came from different parishes, the banns were read in both places (as in your case). This is often very useful, as one entry might give information omitted in the other. What is recorded varies enormously. It can be no more than the names of the couple. You often see reference to the payment of the pledges ("consigned pledges for implementation and performance", or a variation on these words), sometimes reference to the reading of the banns, sometimes the fact that the marriage did actually take place or its date. If it is not explicit in the register that the date is that of the actual marriage, it is best to assume it is the date of the initial contract or booking.
If the pledges had been paid, but one of the couple got cold feet and withdrew, that person lost their pledges, but not the other party. Marriages very rarely took place on a Sunday, so if the date is a Sunday, it is likely that the couple informed the session clerk of their intended marriage when they were present for the weekly service.
