If you search the forums, you can find similar cases that will help with your questions, I do not have all the links and quick replies as I am just a forum regular. But if you search a little you may even find a nearly similar case and have a lot of info for future questions also.
To be fair, there is way to little info in your posts to even guess at your answers. It all matters on many variables with the biggest being your rank, your military status, time of service, time in rank, the type of disabilities and their individual ratings and your desired outcomes.
The only answer I can give you is if you are severed, then you start to receive severance pay the first full month after separation and VA disability the following month. You may have to waive some of your pays to recover costs of receiving both benefits. But again, more information is needed to help you with the recoupment pays that may be required of you.