The Real Bass Exciter is a difficult beast to domesticate.
It does not just boost frequencies, it also make some phase stuff and shifts some frequencies, the guy who made it did not explain all well.
Basically, it may even weaken the bass, and affect negatively other frequencies, if you do not set it well.
The settings I gave you are for the ATH and would not work on the Fidelio.
For the ATH do not touch anything, or you will affect other frequencies or weaken other parts of the bass. Eventually just increase/decrease the boost by changing the value "harmonic energy".
Eventually also you can change the first value, frequency threshold, to 1200 instead of 900 for a warmer sound, or to 600 or 400 for a less warm sound. But check it with different songs, different bass, voices etc to see if you like it or not.
You can save settings on the plugin, and you can also save a plugin chain in foobar. And you can also put and delete a plugin from the chain quickly to see the changes (generally when you put it back the settings are still the same). If Foobar does not reach quickly, you must decrease the value "buffer" in Foobar menu "playback/output". More buffer = no skipping, less buffer = immediate response to eq changes, other changes, and less latency.
1000ms should be fine for most. You may even use 250ms for faster changes if no other program is running and taking lot of CPU.
For the Fidelio you must experiment.
The Frequency threshold value sets the range of affected frequencies. It is not clear how. Generally speaking I saw that 1200 is warmer, 400 is colder. I have the impression that 900 to 1200 are the best values to respect the original sound, at least on the ATH. This anyway depends also on the last two values (the two pre.wave things). If you change those (I do not suggest it) the way the threshold affects the sound is different.
The Harmonic frequency is the frequency which will be boosted. You may know, 40 to 80 hz is the strong part of the sub bass, that's why most people boost 60. Other boost 80 or 90. Subbass = rumble. 90 to 180 is considered mid-bass and affects other instruments, makes the sound a bit darker, gives a bit more punch. 180 to 250 is upper bass, can increase muddiness. The divisions are not universally agreed, and the description is very rough.
The Harmonic bandwidth is the width of the curve of this boost. I understood that a value of 80 here with a value of 60 on the previous value means that the center frequency of the boost is 60, and then the curve gets from 20 to 100 (40 in both directions).
He wrote that for a more quality over quantity boost, and specially with good equipment, lower values are better.
He suggested 60 for the first and 90 for the second. To my ears on the ATH 60 for the second is better quality boost.
The Harmonic energy is the amount of boost.
The two above and below pre-wave should not be touched. He suggested 92 for the first and 10 for the second. I consider 78 and 3 to be better to my ears at least with those other settings and for the ATH.
Have fun.
About Fidelio vs ATH and which one is more flat, you may be right or not. Only a test with dummy head would say. It may be that the ATH have a little push on the mids, or that the Fidelio are a bit v-shaped and have less mids. It may also just be that it is a matter of how this quantity is brought to the ears, and that the ATH have larger and more impactful drivers which give more presence to the mids even if without boosting them in quantity (speaking of EQ curve).
It does not matter after all

Set them as you please
What do you mean for "eq zeroed out"?
You can anyway make presets of eq settings, one for each music (like, flat, little bass boost, more bass boost, etc). You can, as said, also save a configuration of the plugin chain and when you save it also the settings of each plugin will be saved, even if you did not save them in the presets of that plugin.
So you do not need to constantly adjust EQ settings. Nobody does that
The M2BT are a bit too bassy for some stuff to some people. The ATH would not be felt bassy without EQ. That's why they are first in my list. They can please more people, basshead and not.
Real bass exciter was always running, yes, at low push on normal music, bigger push on techno, extreme insane push on dubstep.
I have found anyway other VST which may be giving a better overall sound with similar or even better results on the bass (at least on Techno. For the rumbling sub-bass the Real Bass Exciter is still the best till now). I have published this info on the foobar help thread, on
this and the following post. I am still experimenting.
Nothing to say for spotify and LP, but why should you LOAD things on Foobar? If they are on the Hard Disk, it's there already. If they are on CD, does not your PC/Notebook have CD player? And if you only have CD player in your HI-Fi, does that not have an EQ? Wait for the Angled HM5...
Winner is anyway always relative. Without EQ, each of the two has got its sound signature, you cannot change it, so for everybody wins what get closer to his own personal tastes.