"... have driven 911s" Listen closely: Not. The. Same. a 356, whether original or VW replica will feature 1940s and 1950s technology. But you are doing the right thing: test drive, hang with current owners, ping this club for opinions, of which there will be very many. Go with a reputable builder, of which there may be three. Visit that builder at his shop, face to face. And having it bulit to order is the right way to go, although some here bought used to see what they were getting in to, then had one built to spec once they knew exactly what they wanted. Others with wrenching skills bought kits and made it themselves.
Note: There are what I would call 911 356 Speedster replicas. These would have the 356 FG body and interiors, gauges, etc, but feature purpose-built frame and all 911 running gear: suspension, brakes, steering, trans, engine. Such builds are very very nice and work really well, and obviously depend on a 911 donor. Intermechnica built quite a few of these, and they are sweet. IM not around any more, and i would suppose Beck and Vintage could manage the same. Very pricey way to go, but a truly exceptional ride when done right.