Yes while researching canister filters they are 99% identical all parts are interchangeable. While reading up on them the sunsun was the first then aquatop is supposed to be the US version and there is another one available in the UK.
I've had mine set up for a month now and have no issue have read on this and other sites where people have had them setup for 2 years or more with no issues.
In my own experience the locking mechanism is far more robust then what was on my old Fluval 305, the media baskets on the sun sun interlock to reduce water bypassing the filter media, The quality of the plastics used in the canister are fairly thick and robust the tubing used for water flow is of good quality and quite large in diameter. The only parts that gave me pause are the intake and outflow parts the plastic does feel a bit cheap but should hold up just fine as long as your not driving nails in with them for their intended use they will work fine how often do you really move them around once you have them set.
I've used fluval & ehiem in the past and while I do like them quite a bit I built my tank on a budget and ~90$ for a good canister filter that has a large following and many positive reviews or spend near 200$ for a more well known canister filter that has all the same features minus the UV light just didn't make financial sense and with the money I saved I got the media I wanted and still saved a good chunk of money for other tank related items.
While in most cases I would say that Yes you get what you pay for this is not one of those cases and I speak from the experience of actually owning the product in question. as for the electrical usage the canister uses 35w total with the additional 9w for the UV light, so the equivalent power usage is the same as a common compact fluorescent bulb (spiral type). And the newer models all come with 3 prong plugs unlike some that claim otherwise.
Best bet is to do your research on your own and draw your own conclusions. I have yet to find too many that buy any canister and are not happy with them until something goes wrong weather it be a mechanical problem or lack of maintenance.
Most of the canister flow rates are measured with no media in the baskets a general rule of thumb is to cut the listed flow rate by at least 25% if not 50%. The flow rate decreases depending on how much media you cram into the filter as well as what type of media you put in the baskets. for example 3 coarse sponges will restrict the water flow a lot less then 3 fine felt pads. Also the flow will decrease as the canister gets dirty this is a gradual slow down and can be harder to judge but it does happen, and there is the impeller old or dirty impeller will slow down your flow as well.
As for running 2 filters some do it for extra biological or mechanical filtration or simply for added surface agitation.