Fastening newels so they will last 100 years is a nice thought to have in mind when performing this task. There are some factors to consider to make that idea something like reality. Builder railings, the ones that came with the house, are often wobbly from day one. That's because the posts are often not anchored to the floor at all. Instead they are fastened to a board and the board is in turn screwed to the floor. I have removed hundreds of these and always find brittle drywall screws or just finish nails fastening the post.
To do this job properly one has to recognize the obstacles and solve them. The first is that the post will be as solid as the structure it is fastened to, no more. This structure is a multi layered sandwich of flooring, sub floor, and framing. All were nailed down, all have air space between them. Unless we can compress (eliminate) the air space our newel will be forever loose.
To attempt this yourself, ignore the fastening systems on the market. Instead, use six inch high grade steel construction screws. These should be set at a steep angle downward, inside a shallow inch diameter pocket that can be plugged once the newel is set. The screw pocket should be approx. 2 inches from the floor. A torx head number 10 screw is minimal. Use four, two on each of opposing sides of the post. Predrill your screw hole, set the newel in place and lightly drill a little bit into the flooring on each. Hold the post from drifting while you do this.
Now, add a very small amount of Loctite 8x moisture cured urethane to the bottom of the post. This is optional, the torque and pressure of the screws is enough. Drive one screw in, until it just compresses the pocket slightly and does not move the post much. Drive the opposing screw equally. Repeat on the other two screws. Increase torque on each screw while monitoring the post position, keeping it square and true to the chosen placement spot. When it is dead tight the flooring layers will have compressed tightly together. You have eliminated any looseness and spring loaded the post with the compressed flooring so that it will remain tight for many years.
I have found this results in an astonishing improvement over the common double ended bolt method and indeed any other method I've used. Finally, plug and sand the holes over the screws.