Is Photo useless if I don't want to upload all my pictures?

[class77]

I have 3 computers all running different software(Snow Leopard, Mountain Lion & Yosemite), so I can only run Photo on the newest computer and my iPhone/iPad. I am perfectly happy with my entire library being on my iMac and a pared down version of it on the Mini and iOS devices. I do not have photostream enabled on my iOS devices, because I don't want all my pictures taking up room in the Cloud.

I have lots of pictures that are simply houses/rooms that I would like to use for building a house some day and there is absolutely no need to have them on all my devices. Likewise, I have a bunch of genealogy photos that don't want to be uploaded either.

Am I not going to be able to use the new Photo app on my new rMBP because I don't see the need for the entire library to be in the cloud? Can I keep the pictures locally on the new rMBP using Photo? Can I simply airdrop the pictures I want use the app or am I going to have to find a new app for my pictures?

 

[Weaselboy]

You can use the new Photos app without loading anything to iCloud at all if you like.

 

[Starfia]

Your entire photo library is only stored in iCloud if you turn on iCloud Photo Library. Otherwise, images are stored on the device, like in iPhoto.

Also, according to Apple, photos stored using Photo Stream don't count against your iCloud storage (https://support.apple.com/en-us/HT201317).

 

[class77]

If I AirDrop the iOS libraries to the new Photo library, will the iOS libraries cease to work with the old iPhoto library? I still sync them to my old iMac running Snow Leopard.