I don’t practice much but I have played at 30 of the courses hosting this year and know Myrtle quite well for a non-local (I lived in Myrtle in the summers during college years) so I have seen plenty. My suggestions if they allow practice for the public would be Legends (huge and nice facility) and Barefoot. Hackler which is home to Coastal Carolina has put a lot of money into their practice facility with Dustin Johnson being an alum and still very involved and it is good. TPC is a professional operation through and through which has hosted pro events and has a very good practice facility in addition to a Dustin Johnson academy for juniors if I’m not mistaken. But you might want to call to see if they all the public to practice before heading out. Those are my top picks but I’m sure there are others.