iMac mid 2010. How do I restore Time Machine backup when one of two internal drives is dead?

1. Can I attach an external drive, and do a restore to the new drive configuration that includes 1 internal OS drive and 1 external media/storage drive?

I wouldn't do that, I would simply use Migration Assistant using your Time Machine backup.

1. Will I be presented with an option to select the new external drive and map things during restoration?

Nope

1. If successful, will the iPhotos library be linked or easily linkable to the user account(s)?

When you the Migration Assistant method I explained, yes the library will be linked.

You should replace the 2010 with a new Mac. Then do the following:

When you buy a new Mac the easiest, quickest and most reliable method to migrate from the old Mac to the new Mac is to simply connect the old Mac's Time Machine External Hard Disk to the new Mac using a USB cable before you turn on the new Mac. You will likely need a USB A to USB C adapter, you can find them on Amazon for $10 or less. When you start the new Mac for the first time it will startup Setup Assistant (SA), SA will get to a point where it asks if you are migrating from another computer, select Yes  and follow the on-screen prompts and it's done! It is THAT simple.

If you have already done SA on the new computer then simply connect the Time Machine External Hard Disk using a USB cable and launch Migration Assistant (MA) which is located in Applications - Utilities - MA. Then follow the on-screen prompts. 

The ONLY difference between MA and SA is MA will create a new user account that you need to log into.

Both SA and MA migrate applications (not 32 bit apps), data files & settings. They do not migrate Mac OS itself. Some professional apps such as Adobe and Microsoft apps may require re-installing their apps as they will not allow them to be migrated. As long as you kept the security keys for installing their apps, it is not an issue. 

Finally, never EVER use Wi-Fi when doing Setup Assistant or Migration Assistant. Why, it simply fails in most cases. Please read and follow the directions in Setup Assistant and Migration Assistant. If you do not have a Time Machine backup of the older Mac then create one! If you are not aware of Time Machine, please read Back up your Mac with Time Machine and finally if you need an External Hard Disk to use as a Time Machine External Hard Disk then many experience users on these forums prefer the OWC Mercury Elite Pro due to it's reasonable price, high level of quality and ease of use. 

No worries, let me know if you have any other questions on your migration. Using MA and SA with Time Machine is the most simple method. The difficulty comes when users do things like the old Mac has 1TB of storage and they somehow want to migrate to a 256GB new Mac, no can do!

No