Tissues and bone density vary widely and will significantly effect the results of vibration training...each client responds differently based on their body type and training.
Plates are made with many different surfacea=different haptic responses on each particular plate.
Vibrations encountered in gait are FAR different than those encountered in training, sanders, drills or jackhammers...much of the research done is not transferable...the vibration is completely different.
While I can't give you research, I can point to 15 years of results that indicate appropriate vibration training is highly successful in reducing or eliminating diabetic neuropathy, improving kinesthesia, proprioception, circulation, balance, intrinsic muscle strength, the amount of muscle fibers activated, the degree to which they are activated, strength, power, endurance, cross sectional area of tendons, ligaments, muscles etc etc etc.
When used appropriately there is no such thing as excess...there are limits that can be reached but there are no negative effects when used appropriately or my entire body would be void of any nervous system input. You can train on a platform as much as you train on the floor. High amplitudes and frequencies tend to activate fast twitch muscle fibers while low amplitudes and frequencies tend to stimulate slow twitch muscle fibers.
I'm not sure sinusoidal plates are necessarily the best...maybe to meditate on.
The challenge moving to the future is standardizing how the frequencies and amplitudes are measured as there is no international standard and everyone claims theirs are the best.