If you don't need an optical drive, the MacBook Pro with Retina display hasn't an internal; there is an optional external USB model available. The basic MacBook Pro with 13" display has an optical drive, and several options are shown on the retail store page where you could configure all the extras to see how they add up... http://store.apple.com/us/buy-mac/macbook-pro?product=MD101LL/A&step=config
The MacBook Air series has no optical drive, but has a fast flash solid state drive, is a bit lighter, and has some good possibilities. And it is smaller, thinner, too. The 11" is popular for several reasons. However in the 13" MB Pro without Retina display, you get the optical drive built in.
Most of these support an external display and can use a wireless keyboard and mouse, so when not traveling you could set up a desktop area with all the supporting extras (printer, etc) that you'd need. A good backup system may be an important addition. If you get & use a dedicated wireless base station with built in storage, it can be used by several Macs; but could be handy to automatically backup the hard drive of a portable. Note there are some enticing ones from Apple, at their online store page. I'd consider a separate external drive for backup in addition to any included with a base station; however these wouldn't likely be able to handle the automatic backup 'time machine' function the way a Time Machine unit can.
There also is a possibility you may find a fair deal at slight discount in the Special Deals refurbished section of the online store; but you can't configure these. Some models of computer and portables don't allow the user to upgrade much if any of the hardware, so that is something to look into. Models with a flash solid state drive usually aren't user-upgradable; and those can also have restrictions on when & who upgrades RAM. You can almost expect order or buy a unit that already has whatever upgrades you'd want, done by Apple.
However you may have to do some homework to be sure if you can upgrade any hardware or RAM, HDD or SSD, yourself; depending on your choice this probably is limited or unlikely. An external storage that can also be used to boot the computer (parition the drive, install a clone of the complete running system from Mac) is a fine idea because it can give you an alternative to having no secondary capability to start the computer should there be a technical need to troubleshoot or in emergency (drive failure) run it from a complete backup. A Time Machine won't necessarily give you a complete bootable running system backup.
Since you'd probably need adapters for external displays, etc, you would have to look into the retail add-ons and see what kind of products are available; and keep in mind some of the ports can do a few more things if they have the correct adapter to allow extra functions. See the retail configuration page for say, a MacBook Pro 13" (non-retina) and check out the options. Then see the 'special deals' page and if there is a similar model with optical drive, you would then notice you can't order these parts as a package; but could get them added on to the order from the Apple Store online, or in a retail Apple Store if one is near you.
Special deals MB Pro non-retina: http://store.apple.com/us/product/FD101LL/A/refurbished-macbook-pro-25ghz-dual-c ore-intel-i5
The discount of the 'special deals price' would get you an extended AppleCare plan that adds two additional years on the computer of coverage and maybe some other accessories. You would not be able to order RAM and have them upgrade that for you, in a special deal selection. Or I don't see it offered. You can always call Apple at their main retail number in the store web page to ask various questions, during business hours.
The lower cost of the larger hard disk drive vs the higher cost per GB of a solid state drive, would push me to look into the MacBook Pro 13" w/o Retina display; and it comes with an optical drive. Almost any decent external display could be used to supplement the built-in one, if you choose to set up a desktop situation. The MB Pro can be run with the lid shut and with an external keyboard & mouse. Wireless or wired. The ability to drive an external monitor or display is limited by the graphics support; so see specs to get an idea on that.
Anyway, for writing and perhaps adding graphics or images to a story, the ability to backup your work outside of the computer can take on several guises. Note there is a provision to use a memory card such as a camera has? These can appear on the desktop like an additional hard drive; you can store stuff to them.
A reasonably sturdy, drop resistant and protective case (note weather, too) is also an item to consider.
In any event...
Good luck & happy computing! 🙂
