Changing booktype to DVD-ROM is only relevant for DVD+R media, though...
Apparently it varies a lot how much trouble people have with the burn speed and media brands. I have tested a number of different DVD-R media (including different versions of Verbatim and Taiyo Yuden DVD-R media) as well as DVD+R (booktype set to DVD-ROM), with different burn speeds (1x, 2x, 4x, 8x and 16x). In total I have tested around 150 discs on 40 different games, and I have not had one single bad burn! But again, some other users have reported a lot of problems with this.
AFAIK the issue has nothing to do with the DriveKey chip as such - it is a general issue relating to the burning of media on your PC and the sensitivity of the Wii DVD drive. So the problem should be the same for all users of modchips, whichever brand.
Wrt load times, check out this interesting thread from ther WiiNewz forum:
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