Serger cone thread and regular sewing machine are not the same thing. The serger thread isn't made as strong and is not as heat resistant. Regular SM thread is both. If your machine likes it, then use it as long it passes a breakage test. I just bought a box of thread for $1 and as a former user of of only certain brands, I can't believe I'm using these, but they passed the pulling test and my machine is happy, so what is, is.

I wouldn't use 60 wt. anything for piecing as it's not going to hold it together as well as 50 wt. Similarly, I won't piece with poly. I had issues using poly embroidery thread and melting it with an iron. I stick to 50 wt. Aurifil. It's more expensive because it's one of the best.

Connecting Threads Pro is 70wt and it is made for LA use so it's strong. I use it in my bobbin with all weights and brands of piecing thread and it works great. My bobbin seems to last double the time too. I have over 48 mini spools of Aurifil so I know it's great thread but no better then other quality 2 ply brands and I have some of all of them to compare to each other. If the thread says lingerie or basting thread it is not strong but that is old labeling and not many threads are made weak anymore. The new poly thread made today does not have the problems that the old cheap poly use to have.