Matching rails inside and out, through bolted. You are right, it was a real pain to get everything aligned and it will be a nightmare when they need to be disassembled for rebedding. Rather than trusting wood screws, have you considered countersinking hex head or carriage bolts bedded in thickened epoxy with fender washers and acorn nuts on the inside?

I wish I had seen these Hinkley style handrails before building mine. It's hard to tell from your photo, your example may be the same. These have the base sides slightly sculpted, a continuation of the rail radius. A bit more work but much more elegant than the simple straight sided rails like mine.