The info from Slot Car Corner is worth thinking about. I know that I thought long and hard about tape or braid. In the end I went with the braid, but I plan to keep this track for some time and I put a lot of thought into the designee before I made the first cut. If you plan to keep it for a good while with out making changes to it than I feel like braid is the way to go. My track has not been running very long at this point, but I have been really happy with the braid. Slot Car Corner is in my opinion a good place to buy it as well. They were a pleasure to deal with and it is a quality product.
Lane spacing was another battle that I fought with myself. In the end 4" won. I like the tight racing action and thought of going with less, but I also like to run a wide mix of cars. We run H&R 1/24 and some of them can be rather long wheel base and we run some commercial track cars too. It would be hard to run them on much less than 4". I would say think about what you will be running and what you may run some day before you decide. You can run with more room that you need, but it's not mush of a race if you can't pass at all.
Take a look at my track build
viewtopic.php?f=32&t=10646 May give you some ideas. Most of all have fun.