As per my experience, the import mode usually has better performance than DirectQuery, so I don't think you would get better performance via using DQ mode.
180MB seems not quite huge data, how is the lantency like, 1 second, 2, 3 or even more? In your case, the lantecy is probablly caused by network due to Geography factor rather than import mode.
AFAIK, there's very limited things we can do to improve the Power BI service performance, I'd suggest you sumbit a support ticket. Pro users get free support.
By the way, if you do think the data size may affect the performance, maybe you can try to split the report into reports or import aggregated data.