Is singing along with the record while playing the guitar good or bad?

Hi, Yes, very bad, the music police will come and take you away! No… Seriously, have some fun!

If you can actually play and sing at the same time, good, or great, keep it up. If you aren’t hitting the guitar part like you want to, maybe pay more attention to that and stop singing at the time. But, in the long term, you can help your timing by trying to do both when you like.