I can't comment on Ridetech since I don't have their product.
I have a simple setup on my 67 that I put together my self. Universal Air air bags, ez air ride valves (they are fast), custom made brackets, 2 5g tanks, 2 compressors, 1/2" lines.
The ride with air bags is much MUCH better than stock springs or even some aftermarket. I've had my car sitting on brand new custom made Eaton springs and Bilstein shocks and it still felt like a boat, especially through the turns.
With air bags, the ride is smooth but nice and firm through the corner. I have had my bags on the car for about 4 years now with no issues.
Biggest mistake people make when they install the bags is that they don't provide enough clearance in the front spring pocket and the bag rubs on the frame and eventually blows a hole. If you make sure that bag clears everything you will have years of problem free driving.
Over all if I had to do it again, I would do the bags again on the 67 but I bought my 67 to cruise around with family and not race.
That being said, my 67 is nowhere near as nimble through the turns compared to my 70 Chevelle that has QA1 coil overs on all 4 and UMI suspension, but it's also a different car thats much bigger than Chevelle so I can't really compare the 2.