QFX5120-48Y supports old perpetual as well as subscription (Flex) licenses.
For EVPN-VXLAN, you need the Premium Feature set, which is the middle one. Advanced would be the highest one for this old perpetual feature license.
So actually "QFX5K-C1-PFL" is the perpetual license without any service contract, just the features.
For the Flex license, Juniper made it funny as here the Advanced license is the middle one and the Premium the highest one (in contrary to the old perpetual feature license). Here you have 3 possibilites:
S-QFX5K-C1-A2-3 - Advanced 2 Feature set including Service Contract for 3 years S-QFX5K-C1-A2-5 - Advanced 2 Feature set including Service Contract for 5 years S-QFX5K-C1-A2-P - As well perpetual, but I have absolutely no idea what the difference is between the old "QFX5K-C1-PFL" and this one