Infocom used one block equivalent to 18 sectors (i.e. a single header per track), but subdivided internally to recognise the individual sectors.
RW18 used three blocks equivalent to six sectors each.
Either way, you can't write individual sectors because of timing. You get to write the entire track at a time.
This is not really suitable for general-purpose use.
Now that AppleWin has better tracking formatting support (#125) then I need to see how this copes with RW18:
qkumba said: (ref. csa2)
And @Michaelangel007's repo for Roland Gustafsson's RWTS18 source code: https://github.com/Michaelangel007/apple2_rwts18