Eternal flame of reincarnation and master cubes?

Just to be 100% sure
Flames are for additional options, right?
So getting it would be a very good thing?

Yes, and you can use as many as you want to reset the option untill you get something you want/need.

The system has its problems, but its 30-40 stat boost for every equip you have, however its another thing that makes xenon easier to fund aswell, a lot of people might hate on that part.