Transfer baggage does not need to be taken down and transferred directly to another plane.
I don't think there is any need to worry about security. I've been on both airlines, and it's no big problem. Conditions for air cargo are better. Although the conditions of Air Egypt are not good, Africa is also the largest airline, which is very powerful.
If the airline supports credit card limit payment, it is the same for you to pay in cash in theory, unless individual airlines have special requirements, you need to explain it to the airline in detail.
Comac Com specializes in special fares and acts as an agent for Ethiopian Airlines.