Okay, so the whole Hyrule Field slowdown is the only reason I have finally signed up for the forum because I have found a fantastic combination of things to make the game run 100% all the time, even with my aging i5 2500 processor! I have my setup with the NTSC Gamecube games, so the following is only for that version of the game.
1st, I have one of the latest development versions, don't remember exactly what number, but it has been within the last couple of days. This way, I have the latest fixes for HLE and other improvements available.
2nd, I have been following this thread:
https://forums.dolphin-emu.org/Thread-code-to-review-for-a-boost-in-the-d3d-backend?page=10. I have the latest copy from post #99. you can read up on it, but basically it helps ease the strain on your CPU (similar to what AMD is doing with their Mantle api). Helps add a few FPS and makes things a little extra smooth. Hope the developers merge this into the master branch.
3rd, this is where it can get a little confusing because you have to know if you are going to use OGL or D3D and if you have the NTSC or PAL versions. Between skid (pg.69, post #682 - OpenGL) and degasus (pg.70, post #697 - D3D), you can run either backend with the speed hack re-enabled respectively with their AR codes. I prefer D3D because it seems to run a little better and smoother and the minimap comes out correctly.
I spent several hours last night comparing and trying different combinations of settings, OGL or D3D, HLE or LLE. I prefer D3D coupled with LLE. HLE works, but the echos and ambiance just are not the same as in LLE. Over that time I spent, I went thru several dungeons, wandered about in the twilight, and explored hyrule field completely void of twilight and many other places. I kept at a steady 30fps at all times and the sound didn't skip a beat.
Before finding this combination of things, I was using an old version right before they disabled the ZTP hack, which included the fix for LOZWW textures, version 4.0-619 or something like that. I always would try the latest development builds for the new features and fixes, but would get so frustrated trying to play LOZTP because of the horrible fps (about 9 on my machine). This has made it completely bearable and a joy to play!
Huge thanks to the developers for continuing to improve the emulator, galop1n for making an improved .exe with api enhancements, and degasus for posting the AR code to re-enable the speed hack for D3D!