WS-18 might not be a "new" engine on the Y-20. I think the new engine being refered to is the WS-20 since we already had an all-WS-20 prototype.Actually I don‘t think that‘s correct. At Zhuhai the cheIAF designer himself noted, that currently two domestic engines are in test. As such this is surely the WS-20 but less obvious IMO also the WS-18 and since the Y-20B&WS-20 is quite early in the test phase I see in fact no chance that they are already producing WS-20-powered Y-20Bs. The WS-18 however is de facto a modernised, slightly improved D-30KP-2 and much more progressed in test, so IMO it can only be this one.
The WS-18 is more geared towards the new H-6 variants.