At North Myrtle Beach, the variation in waves is primarily a function of wind direction, speed and bottom contour. Wind will push water into waves in shallow areas. An offshore wind has time to build up wave height as it pushes with the surf motion. A wind blowing from shore out to sea pushes opposite the surf and tends to reduce the wave height. You can check weather forecasts for wind speed and direction in a specific area to decide if it is worth a trip.
Waves will break for longer distances over flatter beaches - the less slope a wave has to climb means a longer run from break to shore. At NMB, the slope of the beach is different at low versus high tide - there will be much longer wave trails at low tide because the beach is much flatter at low water. This regularly changes, though, so you need to see the beach through a tide change to find out current conditions.
btw - if your exposures are for more than a couple of seconds, you may not get just one wave. You may get several. And with the foam going pretty much everywhere, the effect is more like a white fog. It is not like a long exposure on a waterfall or stream that has fixed objects with flowing water - everything is flowing in lots of directions.
It sounds like you have a great reason for lots of trips to the beach to collect data!