I do not think you can change the graphics, changing them changes the raws, and LMP just copies over new raws that came with the graphics packs. But I'm not sure about that.
The settings in the latest Masterwork mac pack have every single option turned on. Meaning, for example, all the civilizations from Fortress Defense are turned on, every race that can be is set to "playable" and all options like harder farming, greedy nobles, and so on is turned on. That is why I recommend downloading the basic raws from the windows pack and replacing your raws with those. You are basically starting out in "nightmare mode" difficulty otherwise, and turning off a hundred or so options doesn't sound fun.
When you turn on more than one playable race at a time, you can select them from the civilization screen of the embark selector, depending on who survives worldgen. With so many hostile Fortress Defense races enabled, its a toss up who survives. Different races have different territory icons, so when you are going through the choices you can get some rough idea who is who. Otherwise try an embark with each civ, you can quit without saving by typing "die" into the terminal.
For a more difficult version of masterwork, I would recommend the default setting plus a few of the Fortress Defense races, like Pandashi or Tigermen. Maybe enable more difficult farming, which makes underground crops take twice as long. The Earth Strikes Back is enabled by default, leave it on for early fun, as stones come alive and attack your miners. You can make Tributes to the various stones, and have your miners sacrifice a large gem, or a specific special gem, and the living stones of that particular type will be friendly when that miner wakes them up. Adopt a cuddly diorite or granite!
Not sure about the black line bug, maybe try changing the display system, it's in the data folder, in init, in a file called, erm, either d_init.txt or init.txt, I think the latter one but I can't remember. Change it from TWBT to default or 2D.