As for the sawzall, the problem is the blade is supported only at one end. If you turn it on, you will notice the tip flops around in a pie shape.
Your right that can happen.
But all of us answering here are quite familiar with sawzal operation.
Regardless of the flopping blade straight cuts can be produced with a sawzall. It's just a matter of practice and not having the 'it can't be done' attitude.
A band saw is easer and quieter but I do not have a cordless one yet.
Bob