How can I adjust the width of the module in Joomla. I would like to show the scroller in 50% width, and other modules float on right of the scroller.

I have tried the Bootstrap size in module options but that does not seem to have any effect.

Would appreciate any help. Thanks

Hi,
Our module doesn't have wiadth of module configuration
If your template includes bootstrap, you can add bootstrap column css class in Module Class Suffix

I downloaded the latest version of extension and the module suffix class is only available in the Grid display. Is there anyway it can be enabled for Horz slider?

No,
It depend module's style of your template
You can see 2 type layout of this extension in our demo site: demo.omegatheme.com/joomla3/ot_ucehelp/
Horz slide still have class suffix class