Hey Bro;
Long time - no see!

I just saw your post and will get the organ experts to answer this for you. But I do know its just a matter of voicing. Algiere's taught me to use 7th chords. But like I said, it just a matter of using the chord that gives you the sound that you want. As for fillers, again, you can use what you want in the amount of time you have to play in between the melody.
If you like, every Thursday between 9 - 9:30 pm we have an open chat and anyone can come. You get get questions answered, such as this and examples to help you out. Its free - so there's no charge involved.
Joy