In regards to paragraph 4 where you ask:

Can I use my phones wifi and cellular data to upload data as photos are also being transfered?

• The answer is yes you can with an iPhone 6. Possibly others too.

In paragraph 5 you mention concerns of photos at your phone being uploaded to a remote service:

• This will happen unless you choose to disable the feature in the EyeFi App. When disabled in the app you will get photos from the card, but no cellular data is used to upload photos to the cloud. Obviously no photos will make it to the cloud with these setting either, only stored locally on your phone. You can use your phone as normal during this time.

I also want to mention that there is no need to setup the EyeFi card to connect to your phone's hotspot, instead use your phone as a client to connect to the EyeFi card through wifi. Your phone will know the EyeFi card network does not have an internet connection and will use your cell network for internet data connections, messaging, etc.

More info: How it worked for us unfortunately realizes your fears

• I recently used this card on a shoot and it worked as you described to receive photos from the card as well as upload them to the cloud all at once, but only by using the phone's cellular data and receiving photos from the card on the wifi connection. We also tried other configurations using a hotspot and computer, but the phone wifi/cellular data method was the best option for us when uploading simultaneously.

• Your best option would be to have two connections if you want to avoid cellular data usage. I believe this is beyond the scope of your question. Look here for more info on that: Super User: When a PC has both a wired and a wireless connection, how is information transferred?

Hope that helps, if you need me to run a test for you with our card let me know and I'd be happy to set it up and report back.