The only units you can use as CLS/AWL commander units are going to be higher-end Nikon speedlights with that capability, or third-party units that include that function. IOW, no, you can't use a Fuji EF-X20 as a "smart" commander. You'd need a Nikon SB-500, SB-R200.
However, a lot of Nikon speedlights do have an SU-4 mode, which is a "dumb" optical mode that lets you fire the flash remotely. But that's all it does. This is known as "manual only" communication. The speedlight would have to be set to M mode, and any settings changes have to be dialled in directly on the back of the flash. You cannot use TTL or HSS/FP (using shutter speeds faster than sync speed of the camera body) with this type of triggering. And you'd still need an on-hotshoe flash unit to fire to trigger the light off-camera.
Most folks today favor radio remote control over "smart" optical communication. This is because optical communication requires "line-of-sight" (the sensor panel on the flash has to have an unobstructed view of the commander signals) and reliability and range can be reduced if you try to us this system outside in bright sunshine. The bright ambient level can overwhelm the commander signal, and there aren't a lot of bounce surfaces around which makes the line-of-sight requirements more stringent. Optical systems work well indoors in studio situations, but radio tends to work equally well indoors or outside.
With radio, you purchase a radio transmitter to use on the camera hotshoe as your commander, and these days, a lot of speedlights have built-in radio triggers, either receivers or transceivers (so they can be either the on-camera transmitter or the off-camera receiver unit in a wireless flash setup). Radio systems can also communicate TTL, HSS, and most of the other features CLS/AWL can, with multiple group control.
Nikon's own radio flash system is limited to the SB-5000. And Nikon looks to have abandoned expanding this system, and are possibly handing it over to Profoto and Nissin to develop. Most of us are pondering whether this means Nikon's getting out of the flash business altogether. At this time, we haven't yet seen flash gear specifically designed for Nikon's mirrorless Z-mount bodies. But it's likely coming from Nissin and Profoto instead of Nikon.
At this time, most folks recommend Godox flash gear if you want to shoot with a flash off-camera. Godox's X system has seven different radio-equipped speedlight models for a Nikon shooter (some manual, some TTL), that come in AA-powered or li-ion rechargeable pack powered versions. And the radio system includes larger AC-powered manual studio strobes, and li-ion battery-packed TTL/HSS location strobes. And most of the lights in the system work with TTL/HSS cross-brand, if needed. So sharing lights with a different-system shooter, or swapping camera systems can be accomplished relatively easily.
Additional 3rd-party radio flash systems you could use would include those from Profoto and Westcott/Rollei/Jinbei. Most other radio flash systems will be speedlight only (Nissin) or studio strobe-only (Broncolor, Paul Buff). Godox is a recommendation favorite because it's lower-priced and more expandable. But it service/support is what you'd expect from a 3rd-party Chinese manufacturer, so take care which retailer you purchase from, since they will be the ones providing support.