Please read the FAQ on the Participation Hub. I think it has a very good definition of what a Foxfooder is.
Could you please tell me which of all the FTP builds is the Flame foxfooding one please?
I may be wrong, but as far as I understand there is no (updated) Flame foxfooding build at the moment.
I think any of both but could be useful convert engineer build to foxfooding build.
Not officialy, but community build, I use these https://box.mozilla-hispano.org/index.php/s/TdZmSxoLVG2aXA1?path=%2FFlame