Can I use a DC-DC step-up module for a small form factor computer?
Without knowing anything about the manufacturer, the DC/DC module looks good on paper.  Conversion efficiency will be down around 80% or less in your application.  At 80%, the input current from the battery estimates at 6.8 A.  Note that converters like this one usually require external capacitors on the input and output to reduce conducted and radiated noise.