I'll say this upfront. For a nano size tank without the hassle of extra plumbing, this does add extra water volume and does allow you to use the unit as a refugium or anything you like to add to it due to a lack of a sump or room inside a sump. I have been using it as refugium with the additions of marinepure to help increase bacteria growth. I currently have the lights set to run 15 hrs with 1/2 hr on before and 1/2 off after the main tank light turn off and turn on respective. I think this somewhat may help PH swing although I can not really confirm for sure given the limited size of this thing, but something is better than nothing imo as my PH isn't as high as I like but tank is relatively stable.
Mount - Yes this could be mounted in the sump area; basically on any stand tank edges. Just make sure you know the dimensions to ensure it fits where you intend to place it. On the Evo, mine is hung from the left side closest to return hose.
Beneficial - This rather difficult to be concern but IMO does help with a little more water stability. Initially I started with 3 macroalgae. I am now left with 2. The other died out which lead to be conclude two possible reasons: 1) the other algae killed it 2) there just wasn't enough nutrition in the tank to maintain all three algae.
Even now with the 15 hrs light cycle, both macroalgae isn't grown as fast as in the beginning. This could be because there is not enough nutrition or enough light intensity. Light intensity is what lead me to purchase a the Finnex Planted Plus LED to see if that is the reason. After running the new light for 7 days, just yesterday I changed the lights back to the original as I noticed during my water changed the pom pom gracilaria macroalgae was slowly dying. You can actually see the whitening of the red color.
Upgrade & Mod considerations - if you want more flow, there is an shiruba PH-103 pump which is adds an extra 22 gph to the unit. I am looking to this within the next month.
Mod - If you use the dividers, due note the dividers blocks water dramatically as macroalgae grows on them. To help, I basically removed/cut some of the dividers out to give more room for water flow.
Current overall thoughts - Since my intent is mainly to reduce nutrition and increase bacteria, my plan to is potentially only keep 1 macroalgae (if one later dies) and use the remaining space to increase marinepure for extra bacteria growth. Really you can get just do refugium with just marinepure.
Looks like I went long. HTH. Would be curious what you end up doing.