This article explains what version of vSRX VNF is supported with NFX150.

Customers who have NFX250 have specific versions of vSRX that are qualified to run with a specific JUNOS version on NFX250.  What version of vSRX can be run to be supported with NFX150?

As of JUNOS 18.1R1 through R2, and 18.2R1, vSRX is not qualified with NFX150.  As an alternative, you can run NFX150 in flow mode natively on vJUNOS0.  The base software is running the same code as vSRX.  As a result of this, vSRX as VNF is not required to provide security since that can be accomplished natively on vJUNOS0 on NFX150.