I've used iSmoothRun for about eight months on a series 4.
If you set up the workouts properly, the app should be able to do everything you want, hands free. With a set workout, splits pop automatically. You can even set it up to have a voice split. No need to press the crown and button.
The app allows for intervals and tempos with warmups and warmdowns and rest periods of any length.
I have not used it on a track, so I don't know if distance tracking is as far off as was my Garmin.
If you were running a measured course and wanted to check splits every mile, you can swipe to the splits/pause/end screen and tap for a split there. What I do occasionally is leave it on that screen, making it easy to tap without needing to swipe. Then the split pops up. The only issue then is that you can't see your running time screen without swiping back to the main screen.
I have encountered some issues with the app. It has shut down mid-run a few times (perhaps because I forced a workout that set up semi-overlapping intervals).
It also seems to measure differently when listening to an Audible book through the watch. On a USATF certified marathon course, miles hit within .01 with Audible off and about .02-.03 short with Audible on.
HR reporting is problematic. While it seems to report reasonably during a walk or elliptical workout, it has problems with runs. Often after a run, the app displays a straight line HR for part or most of a run. The straight line can be anywhere on the scale, high, low or in the middle. There doesn't seem to be a pattern to the odd results. I assume it's an Apple watch issue, since iSmoothRun is presumably recording data directly from the Health app and not reinterpreting it into the straight line.