I assume that you export sound in order to import it somewhere else. This process has a lot of details and used to be done in the step called "mastering" in the old recording days. I'm no expert, but I could try to give you some pointers.
Your first choice is whether to compress or not. The best known example of compressed formats is probably MP3. ...
The two formats seem to be similar, and as the specification says the older wav-format is compatible with RF64.
From what I can see on p 10, the GUID isn't the only thing that identifies the format:
At the beginning of a recording, a RF64-aware application will create a standard RIFF/WAVE or BWFwith a ’JUNK’ chunk as the first chunk.
FLAC is lossless compression. During compression, you can set a compression option: setting this to a higher level creates a smaller file that is still lossless by taking more time to process the file. This compression level is included in the file, so the decoder will know how to decompress it.
So two FLACs created from the same source using different ...
FluidSynth does this fairly simply. The user manual describes the large list of options available to tailor operation, but to render a MIDI file to WAV the simplest command is:
fluidsynth <soundfont file> -F <output file> <MIDI file>
fluidsynth "GT Steel.sf2" -F "high-hopes.wav" high-hopes.mid
Some alternatives ...
WAV files are 32-bit word based, RF64 files are 64-bit word based.
due to the 32-bit basis of WAV files, this led to a size limit (roughly 4GB) which RF64 was designed to resolve.
Yes, they have to be treated differently, although structurally the formats are fairly similar, other than the fact that 64-bit words are used.