You can't compare it with Memchunkhax2 because Mch2 doesn't support sys version 10.4 or above.
10.7 downgrade is almost the same as 10.3, the main difference is "sysupdater.3dsx", so just find a proper sysupdater with memchunkhax2.5 (I guess this is what it should be called?) and follow the normal downgrade guide.
Please correct me if I'm wrong at any point, I'm still in learning process.