If you look on the spool ends you should see the ply of the thread. Usually it will look like 50/3 or 60/2. I'm not sure what ply the serger thread is and it doesn't say. Serger thread is thin like a 60 or 70 weight thread.
Maxi-Lock is polyester thread and Signature is cotton. I have no preference between the two. Just depends which one has the color I need.
I run serger thread thru my domestic machine all the time. I like using it over regular thread. Because it is so much thinner when I press the seams I don't get a "ridge" on the seams. It presses much flatter.
If you do use it in your domestic machine, you will need to adjust your bobbin case tension.