First, the tank looks good partly because I just set it up and put Lincoln in.
However, with one fish and good filtration, it should stay pretty clear indefinitely.
There are different morphs of Bettas. No idea what Lincoln's morph is, but he's a cool guy. Some have longer fins and different colors, etc.
https://www.tankarium.com/types-of-betta-fish/
This site above had some cool info.
Secondly, I like your setup and LOVE Goby's. They are awesome little fish! I don't know what a Gramma is.
Keep us posted on your tank!