Awesome. See, you learn something every day...yes those are beast motors and a lot of guys are using this size for long range 7" build. I'm actually doing a build now with the XL7 frame and using the new BrotherHobby Avenger 2507 1500kv motors.
What is the importance of the numbers on the motors, such as 2204 or 2208?
This is not a straightforward questions, there are hundreds of variables. The only suggestion I have is to do a few hours of searching the internet. Go to Rotorbuilds.com and you can see thousands of builds complete with detailed parts lists. You'll even see a few I've done including this Catalyst Machine Works Smooth Operator I just finished not too long agoHow can I understand the motor and frame are compatible?
I've heard good things about that frame, looks greatCatalyst Machine Works Smooth Operator
This is not a straightforward questions, there are hundreds of variables. The only suggestion I have is to do a few hours of searching the internet. Go to Rotorbuilds.com and you can see thousands of builds complete with detailed parts lists. You'll even see a few I've done including this Catalyst Machine Works Smooth Operator I just finished not too long ago
View attachment 2990
As you can see above, I'm not the expert I can tell you what they represent though.
The first two numbers are the circumference of the bell, and the second two numbers are the height of the stator. Together they define how large a motor is. To get the "displacement" for lack of a better word, you can multiply the two numbers.
For example your 2507 is 25x7 = 175
2408 is 24x8 = 192
Different people like different sizes for their personal application; it comes down to preference and how you want to fly.
This guy doesn't really do long range, but I appreciate his analysis