Well to answer your Tubescreamer question, get a TS-9 and mod it. I have had a phathead and a TS-9. If you want a tubescreamer sound, TS-9 is the best choice. The mods are easy to do and easy to find on the web. I just changed one cap and it holds all the low end.
I know nothing about synth :/ sorry.
High gain and Low gain fuzzes are really more about how each pedal is set. You could make your muff do both. A muff variant is almost always high gain, but it can be low and softish.
As far as OD>Fuzz and vice versa, you just have to try it and see. I use a TS-9 at high gain into a EHX Tube Zipper set at low gain. Amazing layering and Amazing seperate.
When your trying to find a sound to call your own:
1. Dont follow the rules.
2. Dont make your own rules.
3. Dont use the sample settings you find in the manual.
4. Have fun

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