I recommend not getting this, the Kurutoga Advance is better built, and the mechanism is better. The Switch has a horrendous level of noise when in Kurotoga mode, while the Advance is much much more negligible. It makes it worthwhile to not have a Switch, because what is the point of Kurutoga mode if it feels bad? Just get the Advance
This is only worth using In either .5 but better yet use it in 7 so that in rotation it's reduced to a .35 give or take and it's very strong, with .5 it's a little fragile but usable and the .3 is useless. The .3 is only good in the del guard and orenz since they keep it from breaking.
I don't know about it being that good. I had a couple of these but after I got my Pentel Orenz Nero in .3 basically every other writing utensil I owned got put on the bench.
Not sure about the specific number of holes, but I thought the space in the middle was to make it friendlier for left-handed people who hate feeling springs as they write