Does vfw not support video filters in the command line options?
I've tried using the syntax available and cannot initialize the codec when encoding.
I'm especially interested in the resize filter syntax.
If you mean --vf / --video-filter command line options than no, they are not supported in vfw. Filter system is part of x264 cli not part of libx264 so this functionality is not available through it. Also I don't think it is good idea to mix filters inside codecs (it can be ok for x264 cli because it more than encoder but not for x264vfw).