I suspect that the preference for filioque over et filio and ac filio has more to do with maintaining the creed s singability rather than introducing any fine distinctions in meaning None of the distinctions I m aware of which are small indeed alter the meaning in this context at all Et filio depending on context could be construed to mean thus from the son or from the son too or even from the son none of which really apply here Ac filio in a different context could be construed to mean since from the son as well as and from the son Filioque can pretty much just mean and from the son in any context it can not ever imply any thus or since When que et and ac are mixed together generally et has higher precedence than ac which has higher precedence than que but in the creed issues of precedence don t come up since these are not mixed together into one phrase So far as I can see the only distinction between one choice of conjunction or another in this context would be entirely aesthetic