Oh, gotcha, thank you! I do apologise in this case then, raycasting would not be an appropriate solution for what you want to achieve especially since with the context you would have 3D spaces to check for.
In terms of the original question, yes, ideally you don’t want to be polling any Region3 method whether or not it’s a raw Region3 method or a module that incorporates it like ZonePlus. I don’t imagine there’d be any logic you want to run while the object is in placement, but if there is then you might want to consider FindPartsInRegion3WithWhiteList.
I would never endorse using any method supporting Region3 without a whitelist, it’s just too computationally expensive if you intend to run it frequently. At that point if a whitelist doesn’t work I would just use pure math to check the position of the current object and see if its within the bounds of your area. I think Roblox has a method coming later that’ll make this process easier.
As for checking when the object is placed/added into your area of choice, you realistically would only need that region cast to happen one time and then you can cache the result of where that object was placed in but I’d still encourage the above whitelist method so that your Region3 isn’t casting over parts that are irrelevant to your placement or the region. You should be fine after that.