One thing I would add to this - there is a risk continually running power into a power bank. The design of these things will have a circuit to manage charging, but it's probably not been designed to be charged on a continual basis. And most use cases would have expected charging and discharging to not happen concurrently. That's not to say it can't cope with it, and it probably can. But if there was a failure, the power density in Lithium based batteries usually ends up with a runaway thermal condition that results in fire. If you compare a powerbank with a UPS, the UPS design is obviously more focussed on providing the protection you expect for this kind of application.
If you wanted to minimise your risks, I would suggest ensuring you have a reputable brand of powerbank where the charging circuits probably are more robust, and not something a bit cheaper/unknown brand, although one gotcha you have here is that they might not support charging and discharging at the same time. And consider hosting the powerbank in a metal box, so that if the worst were to happen, it would likely be contained.
I've seen a few too many incidences of where equipment with Lithium batteries have met an unfortunate ending and an increasing number of domestic and commercial fires have Lithium batteries as the root cause.
For example, my Ecowitt outdoor AirQuality detector, which should charge via it's solar panel, it has a micro USB socket to be able to top up the power in the internal battery. Ecowitt do not expect you to provide a permanent power supply to the USB port, but expect you to provide a power top up from time to time when the batteries get low. Because I'm lazy I've run a permanent USB power connection to the unit, but I don't give it power 24/7, but just a boost of power for an hour once a week so it gets charged in the manner that the original designers expected.