It depends on which entity is coining the phrase, but in general, "Smart Queue QoS" is most widely known as the "knobless" method for controlling against bufferbloat
, via a combination of a packet queuing discipline (arguably the best of which is CAKE
, as has been adopted by OpenWRT, or second best but more widely implemented being fq_codel
) plus a hierarchical rate limiter (HTB, for example).
One of the best examples of a decent implementation of this (which was far ahead of Asus or Netgear when it was first done) is Ubiquiti's "Smart Queue" QoS on their EdgeRouters; it's basically just a combo of fq_codel and HTB. You only need to turn Smart Queue "on", specify upload and download bandwidth (you can/should tweak a lot more, like quantum #, etc.), and assuming your CPU has enough power to push packets at that aggregate speed (SQM is typically non-offloadable in most CPU architectures), you're good to go.
As far as Netgear and Asus go, I believe their latest stock firmwares off at least fq_codel as a choice for your queuing discipline (qdisc), probably listed under some consumer friendly name like "QoS Method" or the like. I believe certain Asus models (and usually Merlin) offer at least fq_codel, if not more options. So it's a "mostly yes" to answer your question there.
SQM, when implemented properly, tends to improve average latency and jitter by a factor of how different the speed is across interfaces, multiplied by how often you're saturating the WAN link; for example, it tends to help the most when going from a 1Gb/s LAN pushing 50Mb/s of would-be up+down WAN traffic onto a 25Mb/s DSL line. I would still help, albeit a little less, when ingressing/egressing 100Mb/s of Gb LAN traffic back and forth to a 200/20 cable WAN, and is least likely to help when going from that Gb LAN to a cable or fiber link of almost the same (or same) speed, presuming the link isn't being saturated that often, if at all.
As it is with anything else, it can definitely be a benefit when used properly, but it's your responsibility to know when and how to use it best.