Drywall paper tape bubbles

This may be a stupid question but, what is the standard length of a wood stud for an 8 ft. wall? ... a 10 ft. wall?

Hello, I purchased a property a month ago. I'm a single mother, handy with the right guidance and grateful for these forums. Unfortunately, to my untrained eye I did not realize that the previous homeowners had painted over wall paper many times in almost every room in my home. How can I cover the seams and cracks in the paint on the walls currently? One suggestion I received was to smooth over the entire surface with spackle then paint. I was thinking of smoothing over where the seams and cracks are with spackle and possibly use a sand paint to add texture and hide any imperfections? Is there a better solution? Please keep in mind, I have two small children so I will have to take one room at a time and want the least mess and spackle dust possible. Thank you.