No need to guess - you can go look (link below)... Pretty much all zwave devices have published Configuration Parameters on the zwave alliance webpage.
You may be astounded by some of the things devices can do that aren't exposed in the built-in HE driver... For instance the 14294 support Double Tap commands (like a scene controller) if configured correctly (and a driver that supports this installed in HE).
That is why I WISH that HE would publish their in-box drivers. Then if we wanted just ONE of the excluded features, we could easily add it with much lower risk of a bad driver messing up the system. For instance my custom 14294 driver that does support all parameters doesn't work over hub link - some refresh issue probably. Don't know why, as it works perfectly in ST. If I could see the HE in-box one, I could fix the custom one in probably <5 minutes...
Anyway... Back to your question:
14291: It isn't a dimmer, so no adjustable dimmer rates on this... Product Configuration Capabilities
14294: Product Configuration Capabilities
Remember there are 3 sets of dimmer settings, not 1. Digital, physical, and all on/off. The all on/off isn't used much, though,
Make sure you are changing the right one for the type of on/off command you are using. If you only do 7 & 8, that has nothing to do with behavior when turned on/off at the wall switch.
Param 7 = Digital dimming # of steps (1-99)
Param 8 = Digital timing for steps (1-255)
Param 9 = Manual/physical dimming # of steps (1-99)
Param 10 = Manual/physical timing for steps (1-255)
Param 11 = ALL ON/OFF dimming # of steps (1-99)
Param 12 = ALL ON/OFF timing for steps (1-255)
