I'm a couple months late on seeing this, but I thought I'd post anyhow to add a little info for anyone else.
I have no personal experience with septic systems in North Carolina. I'm going based mostly on what little I've looked through the NC state septic rules (Chapter 18, Subchapter 18A, Section 1900, for reference), so feel free to correct me.
It appears that a Type IV system is:
a. Any system with LPP distribution
b. System with more than 1 pump or siphon
I then assume that a Type IV-B has 1+ pump. Either way it sounds like a pumped system. According to the table on pg.50 of the rules, the minimum inspection/maintenance frequency for that kind of system is twice a year. As to being able to inspect it yourself, I'm not sure about that.
Sand lined trenches sound like a form of soil-substitution, where existing soil is dug out more than you usually would for lateral lines and then some amount of better soil is put down inside the trenches or bed to provide better infiltration for the wastewater. It's basically transplanting good soil into an area with bad soil or bad drainage. As to how well this kind of system performs, I have no idea. Considering the high inspection frequency, it sounds like there's either a higher likelihood of malfunction or under-performance, or a higher concern that such a system will malfunction or under-perform.