IIRC, with Dolphin a number of GC and Wii games are fairly even when it comes to hardware demands, so it's not as if GC games are always easier to emulate, and Wii games harder to emulate. Some titles, F-Zero like admin89 mentioned, are more demanding than a lot of Wii games.
The best settings for every game differ; your best bet is to look up that specific game. The forums here have many game threads in the Game Discussion section. The Dolphin Wiki is another great resource that offers some suggested settings, and it tells you what specs users had along with their performance. It's useful in determining what to expect with your own system. For example, check out the Mario Kart Double Dash!! wiki entry. I'm sure it'll prove handy, well, as long as the game you're looking up has enough info.
Post your settings as text or screenshots, and then we can probably tell you what's generally good to enable/disable. Press the Config button and look at the General tab. Also press the Graphics tab and look at the General, Enhancements, and Hacks tabs. Those are where some of the most common configuration changes occur.
The best settings for every game differ; your best bet is to look up that specific game. The forums here have many game threads in the Game Discussion section. The Dolphin Wiki is another great resource that offers some suggested settings, and it tells you what specs users had along with their performance. It's useful in determining what to expect with your own system. For example, check out the Mario Kart Double Dash!! wiki entry. I'm sure it'll prove handy, well, as long as the game you're looking up has enough info.
Post your settings as text or screenshots, and then we can probably tell you what's generally good to enable/disable. Press the Config button and look at the General tab. Also press the Graphics tab and look at the General, Enhancements, and Hacks tabs. Those are where some of the most common configuration changes occur.