What should be ideal relationship in schedules

What should be ideal relationship in schedules?

No solid rule applies. Here is my order from best to worst:  FS -- As much as possible -- This is, as mentioned above the most defendable and causes the least amount of progressing issues.  SS and SS +lags -- as long as the lag is reasonably short relative to the predecessor activity  FS -lag - as long as the -lag is relative short to the predecessor activity.  FF only where you really need the successor activity needs to finish at the same time as the pred.  FF+lag will work much the same as FS-lag,  There are good use of a SF relationship in a continue process operations schedule where a successor shift (or task) must start prior to the completion of the pred activity. However, in the Construction / Engineering industry it causes more problems than it solves. Therefore, I would agree to avoid this relationship

There are no ideal links or relationships. It doesn’t matter what kind of links you’re using as far you’re logic between activities is OK.  It depends if you’re using CPM where you have ‘finish to start’ links for the most part a logic between activities, I call it a ‘train-wagons-logic’ with sometimes a ‘start to start’ link or, not on the same activity, with a ‘finish to finish’ link. It’s also allowed to use a ‘start to finish’ link.  In a PDM / Precedence activity method you can have between two activities a ‘finish to start’ link or a ‘start to start’ link or a ‘finish to finish’ link or a combination with a ‘start to start’ and a ‘finish to finish’ link. It’s also allowed to use a start to finish link.  The point is you can’t express logic using CPM the way you can express it with a PDM. But important is: an activity network has to be closed which means: one open start activity and one open end activity. That’s the benefit of PDM, you don’t have to use dummy activities.