I've never been a fan of HOB for refuges for nutrient export. The volume of macro you can keep in it or amount of LR etc is too small to be really effective. They can be good sources for pod production though they do come with some risks. Those risks are siphon failure if its a siphon run design or outlet blockage if its a pump driven design. If its a small HOB and you want to get the most out of it, put some LR pieces in it and leave it at that as it will provide the pods a place to hang out, bump uglies and reproduce without fear of getting eaten.
You can add a little bundle of cheato, but I would avoid the other macros as they are more likely to clog the drians. Cheato can do it too, but tends to stay put better. As far as light goes, do a reverse cycle as it seems to work the best for you on both pH and growth for the macro.
This is not the best solution for a refuge, but it gives you some benefits. The refuge serves many purposes, a safe haven for pods, a place for macros to grow for nutrient export, a pH balance device and also additional water volume for better stability. A HOB will give you elements of most of those except the water volume. I think the water volume is the greater benefit, along with the macro isolation but that's just my opinion. In a smaller system, the isolated pod population is important only if you keep pod predators like mandarins for example, or some of the wrasses like the Leopard.
If you go full-time light, set the timer for a 2-3 hour period of off time during the early morning hours or late afternoon. That will give your macro its off period. If you use anything other than cheato, make sure you trim and prune it on a regular basis as both the brief darkness and trimming will reduce the risk of it going sexual on you.
Just be aware of the possible failure points.
