In order to use those mics, however, you'll need to purchase a separate interface with an XLR connection and phantom power, which sends electricity to the condenser mic's preamp. This interface from iRig (a company we'll return to in a second) will connect and power a condenser to your iPhone without breaking your budget.
If you want to record directly into your phone using a line-in, you can also buy an interface (not just an adapter) that allows you to plug a quarter-inch jack directly into the lightning port in your phone. This will allow you to use software like Garage Band to record your electric guitar.
FL Studio Mobile is another DAW you may want to consider if you're looking for an experience beyond just Garage Band. Like the desktop version, FL Studio Mobile comes with baked-in effects like audio compression, delay, phasing, and more, all with FL Studio's intuitive interface. You'll be flying without some of FL Studio's best tools (like their Edison audio sampler), but for a mobile DAW, FL Studio is a good mixture of simplicity and capability.
While there's plenty of other hardware you could add to your iPhone-centric home studio (perhaps an Orba?), a microphone, interface, Garage Band, and some decent headphones are enough to get you up and running with enough tools to record just about anything short of an entire drum set, orchestra, or brass band.