In the forum, we usually use the term “pocketsocket” for the plug-in kind to distinguish them from in wall outlets or micros, since different manufactures use different terms. 
Different ones have different features and very different prices, and so they will work for different households.
You can see the comparison of some of the features in the device class features FAQ (the topic title is a clickable link)
As repeaters
Pocketsockets are very popular repeaters Since you can easily put them pretty much anywhere. Remember that zwave repeats only for zwave and zigbee repeats only for zigbee and you need a repeater about every 40 feet or so for zigbee and about every 75 feet or so for Z wave plus.
The iris 3210 smart plug was unusual in that it was a zigbee on/off plug that also had a Z wave repeater. But most pocketsockets are one protocol or the other.
People often ask if the device will still repeat even if it is turned off, and the answer is yes.
If you’re going to put one near a zwave lock, make sure that it supports “beaming.“ most models made after 2017 will, but if it’s a very inexpensive device, just check to be sure.
https://thingsthataresmart.wiki/index.php?title=Beaming
Energy monitoring
Although energy monitoring is a popular feature for pocketsockets, it’s really not a good match to a mesh protocol like zwave or zigbee. These protocols are intended for tiny messages sent infrequently, like a light switch that is used two or three times a day. If it’s OK if you are truly using these for energy monitoring and you’re only checking them every hour or so.
But as soon as you start checking them every five minutes or every minute or, heaven help us, even more frequently, you increase the traffic on your mesh network by literally hundreds of times. This condition causes other messages to not be able to get through and adds lag to your entire setup. 
Seriously, if you want to crater your entire zwave network, put two aeotec energy monitoring pocketsockets in the same room. They will try to use each other as repeaters and if you have them sending back reports on energy usage every minute so you will get them ping-ponging back-and-forth. 
Instead, if you absolutely must have near real time energy reporting, use a Wi-Fi pocketsocket for this instead.
WiFi pocketsockets
Wi-Fi pocket sockets, particularly those imported from China for use with voice assistants, are frequently really cheap and, as just mentioned, are better for real time energy monitoring. But they also often lack safety certifications, Wi-Fi inherently uses more energy than zigbee or zwave, and many home routers can only handle 30 Wi-Fi devices total including all of your phones, tablets, game players, etc. So for most uses it’s better to use a Z wave or ZIgbee pocketsocket.
If you just want a couple for near real-time energy monitoring, no problem. Although I would recommend getting one with either a UL or Intertek ETL safety Mark.
Also, if you’re concerned about privacy, do not use any device that requires a Chinese server for its cloud or a Chinese app to set it up.
New Chinese Law Allows Govt to Legally Hack any Internet Op Inside China (including IOT clouds)
Inexpensive zigbee pocketsocket
Often people are looking for an inexpensive zigbee pocketsocket to act as a repeater to improve performance of their zigbee battery operated sensors.
There didn’t used to be a lot of these, but now Ikea has added some in their Tradfri line which are a simple on/off device and quite inexpensive. $9.99 in the US and £9.99 in the UK. They are also available in other European countries with the appropriate local socket style. They work very well as zigbee repeaters with smartthings, and even work well with Xioami sensors, which is unusual. The IKEA smart bulbs and pocketsockets work well with smartthings. The handheld buttons and remotes only have a partial integration at this time.
The initial reviews on these devices were low because people were expecting them to also work with HomeKit like the smart bulbs do. But looked at just as a zigbee device, they seem to be fine.
https://m2.ikea.com/us/en/p/tradfri-wireless-control-outlet-30356169/
Again, there are lots of other brands to choose from which will have more features or at least two sockets, But if you are looking for a pocketsocket primarily because you want a zigbee repeater, this is a definite candidate.
Another good place to look for less expensive zigbee pocket sockets is on the list of echo plus compatible devices that have “smart setup“. Amazon keeps a list of these which you should be able to get to from the product description page for the echo plus. But those are still all likely to cost more than the IKEA one.
Two independently controlled sockets?
If you want two independently controlled sockets, there are Only a few choices.
The most popular is probably the new Zooz Zen25 design, but you will need a special device type handler in order to get the independent control.
Read the Specs Carefully
A couple of safety notes to be aware of.
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never plug a device with a motor like a blender or a vacuum cleaner or a fan into a pocketsocket dimmer. Most manufacturers will call their devices “appliance modules“ if they can handle motors.
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even if a pocketsocket says it’s for appliances, read the specs carefully. US code in most places requires that an in wall outlet be able to handle up to 15 A. But many pocketsockets can only handle up to 10 A. Take this limit seriously.
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I don’t know of any pocketsockets that can handle up to 20 A, Which is something you might need for a refrigerator or a window air-conditioner. Again, take this limit seriously. There are some in wall micros and in wall outlets that can handle this higher limit.
Many smart home manufacturers sell primarily to the European market where appliances like washing machines use much less energy. So even if a pocketsocket description says it’s for washing machines and fans, read the specs.
And again, different devices have different features, so it just depends what you like best.