I'm a strong believer in larger cool water (tap water) tanks that have a central circular 'filter' in which the water naturally lifts and is pulled into the air with an enclosed fan. The unit has a monitor that measure humidity and can be set to maintain a specific level.
Warm water systems can quickly increase the level of humidity, but have problems with other solids falling out of the water into the filter and can have problems with mold. So, I avoid using them.
We have a high-tech constructed home, which greatly slows the change between outside air and that within the home. We find at 70 degrees F, that we hold humidity level of around the mid-forties. High levels condense out on the windows on colder days. Our Home has the Humidity unit as an attachment to the Forced Air Furnace, which greatly mades things much simpler.
We have a portable unit (as defined above) at the cottage. I would be happy to provide you its name when I visit again in a couple of weeks.
It is important to remember that humidity flows from a room into other parts of the home. Much like what happens after a shower when the warm humid air from the the shower flows out into the home. Hence, it is important to upsize the unit beyond the size of the bird room.