There is currently no way to completely disable info box (or i am blind).
The only option is to manually disable it for every boss encounter which is not very handy.

What version of BigWigs are you using? (Stating 'latest' is not useful)

121.4

There is no option for it.

The underlying problem is important to us though: Why would you want to completely disable it? Does the info box never provide you valuable information?

No plans for this. The information displayed can vary wildly boss to boss. One can be useful one might not.

I prefer minimalistic UIs, i need only timer bars and sound alerts.
Everything else brings me nothing but distraction.
Its rather strange to say use all we got or nothing. I think its the user who decides whether he needs info box or not.

I think its the user who decides whether he needs info box or not.

They do, on an individual basis, since every basis is a different feature, provided through a central frame.