Being from SC and boating these lakes though out my life I'm not crazy about Moultrie, Marion is nice. I just spent a week on Lake Greenwood (only about 11k acre, 220 miles of shoreline). This lake doesn't have much boat traffic at all! It's small in comparison, long and narrow, we had a wonderful time boating all day and seeing about 20 boats, mostly fishing. First time I ever saw a ski nautique tied up to a bridge fishing
From what I could tell housing around Lake Greenwood was very affordable. Not terribly far from Greenville which IMO is a very nice city. Greenwood has a lot of golf around the area if that's your thing, and Lake Greenwood has one of the nicest Class A RV Resorts in SC, that is where we stayed.
Lake Murray gives you another option, I grew up on this lake, moved off about three years ago. Home prices are back on the rise, sizable deep water lake (50k acre, over 500 miles of shoreline), depths to over 200 feet, tons of boat traffic in the summer. I now avoid the weekends during the summer months. Gives you the Capital city only 20 minutes away (depending on traffic and your location), maybe it's me but growing up in this city it doesn't have much to do unless your a Gamecock fan. Most everything revolves around the university. Greenville is *much* nicer IMO, Greenwwood has that small town feel, has most everything you would need. Charleston is very nice, I just hate the tourist traffic in and around town.
Good luck in your choice!
Steve