No, if you read the guide you have installed OMV on Raspbian Desktop not Raspbian Lite, Raspbian Lite is 'headless' no desktop installing OMV on Lite will give a WebUI to manage OMV.
Desktop installs deploy 'extras' which are totally unnecessary and will conflict with OMV's operation. So there are three choices;
1) Carry on as you are
2) Remove OMV and use Raspbian Desktop which is just as configurable
3) Follow the guide install Raspbian Lite and then install OMV
in respect of the first two you're on your own as no one on here will have a solution as there simply isn't one. Option three has been tried and tested, including by myself, what we don't support is a raid configuration via USB.
With new information I have more questions. Please be patient with me
So, do you think or do you know if is availible power manager in WebGUI for USB discs when I will install Raspbian Lite? And same question for SMART diagnostic.