TC or External HDD for back up and storage

Hey there,

I have

- an iMac 21,5" late 2012 2,7 GHz i5 processor 8GB RAM NVIDIA GeForce GT 640M 512MB

- a MacBook Pro 13" mid 2009 2,53 GHz Intel Core 2 Duo 4GB RAM 1067 MHz DDR3 NVIDIA GeForce 9400M 256MB

- a MacBook Pro Retina 15" mid 2015 2,2 GHz Intel Core i7 16GB RAM 1600 MHz DDR3 Intel Iris Pro 1536MB

All are running OS X Yosemite 10.10.4

Using the iMac at home, the old MacBook Pro when away.

Since I need to be able to work on the same files on both these computers, I have most of my documents stored on a LaCie 1TB USB 3 external HD so I have my documents at my fingertips both at home and away. I keep a copy of these files in a folder on my iMac and make a back up to this folder every now and then manually.

I will throw a lot of documents that are still on my old MacBook away and I want to move what I wanna keep onto my iMac or my new MacBook. How can I do this in a most effective way? I would manually just drag folders from my old MacBook onto my LaCie Drive, connect this one to my iMac or new MacBook and drag them on there... Using Migration Assistent would probably be a better idea, no?

Also, the manual backing up thing is not really the way to go, since I am only backing up the files I am creating and/or working on, nothing else. Would using Time Machine to back up to Time Capsule be a good solution? The WiFi-network at home works fine, so that wouldn't be the reason to get a TC. The wireless backing up is kind of appealing to me (since there are no cables on my desk at all). What with the files I want to keep on the external HD to take with me when away? Is there a way to back those up automatically as well? I know I can attach 1 USB external HD to the TC through USB but apparently it isn't backing that one up. How much of a solution is storing stuff in a cloud on option?

I have been reading user reviews on TC, I have been reading through solutions on here as well, but since it is pretty specific, I am not sure what to do. I have been working with Apple products since 2009 and kind of know what I am doing (things I need to do), but I am in no way an Apple geek. I am happy it does what it needs to do without me having to do a lot of stuff (backing up, installing stuff, updates, ... ) as opposed to my former Windows based computers, I am happy Apple does all of that for me.

Any ideas, experiences, tips, tricks,...?

Thx in advance!

J