Is there any way of knowing which engine strategy is used?
It should be written in the output loogs when jsreport is booting.
Do you know which the worst bottlenecks are?
You should see the timing for specific parts of rendering when you hit debug in the studio.
In most of the cases the chrome makes the most of the time and other optimizations are not so much worth it.
More CPU speed should help though.
However, take your time and test what works the best for you.