So Matt, what you're proposing here is that the Ecclessia and Lothanasa, as well as other religions acknowledges the same "creator", but each one with their own vision of it, and perhaps also dogmas?
As you said that is what happens in the real world, where many religions have/had the same concept of a "Creator", but with varying details, or so to say.
That is, Eli, Illuvatar, Yahveh, etc.
Different names, different beliefs, different dogmas, but none of them "true" per se. But the "Creator" is there. That's what i think it may be good for the setting
I think it's a good idea leaving the real fate of the mortal souls as a mystery.
That being said, the same way the LB pantheon keeps them in their own planes for a while after said mortals die, other potential deities may do the same, and not necessarily with the same objective (Gaining power).
For example, lets assume that Tigner's eastern gods are separate beings from the LB ones.
The LB gods are higher beings, so in the same way others may exist.
These eastern gods may have their own realms where they may take the souls of those faithful to them. To reward them, or to punish them, doesn't matter what.
But also then, instead of keeping the souls captive the same way the LB pantheon does, they may simply reward their followers in life (Like Velena does), and not interfering in any way with their afterlife destination.
Going back to IRL comparison, many people have also worshiped not only "invisible" or otherworldly gods, but also actual tangible and recognizable people or things.
Egyptians saw their Pharaohs as gods if I'm not wrong, so following this example there may be a place where a really powerful wizard, or even a higher being in the mortal realm is considered a god by some people (And honestly, in a medieval setting that's nothing weird at all).
Just an after-midnight brainstorming, but i think it's a good idea :)