Are there different levels of phimosis?

Yes. Some phimoses are so tight that the foreskin balloons with urination because the phimotic ring is so tight. Others can be so mild to cause minimal discomfort when retracted. Most cases have various degress of foreskin narrowing between the two extreme examples.
Yes. There are different degrees of phimosis depending on how tight the foreskin is. Phimosis is tightening of the foreskin which prevents full retraction of the foreskin.
Here are some ... Although phimosis is coined to strictly denote the inborn presence of long, tight, non-retractable foreskin, it has been clinically and loosely used to cover the full range of real phimosis to long, redundant, but still easily retractable foreskin. The real issue for "phimosis" is how its presence bothers personal life, which deserves medical attention and timely care. .
See below. Phimosis in general means that the foreskin cannot retract to expose the head of the penis. It may or may not be symptomatic. If symptoms are present, it is usually pain with retraction or manipulation of the prepuce, sometimes with bleeding or cracking/fissuring of the penile skin. If the skin can be retracted to expose most but not all of the glans, then i guess one could consider it "mild".