Being Respectful in Life Lessons

Ok, More advice needed....
I am 21 and a female and my Fiance is 20, I still live with my parents and I have always been very respectful to them (always avoiding fights and confrontation)- and my fiance lives around the corner in my parents rent house (we plan to live here after we are married)
The wedding is August 15th 2020
my parents are paying for it
but my parents have been very controlling over the wedding planning (more in last post)
my parents think my Fiance is immature and super controlling over me and they keep telling me its my decision and I don’t have to marry him and how they never get alone time with me because he is always around - my mom told all my family that he is pressuring me into things I don’t want in the wedding (really she is the one doing this) and making me stress sick
my Fiance wants to stand up to them but I don’t want him to be an immature jerk about it and I don’t want them to be upset with me after he leaves for the night…
we plan to live here after the wedding and I don’t want it to be tough then, Fiance is to the point he wants to move back to his home town 3 hours away, but that’s not what I want for many reasons…
so really i just don’t know, should I let him stand up to them and risk a huge fight? Are my parents right about how he shouldn’t have a say in the wedding plans? Is my fiance just being immature? How do we solve it? Does fiance need to back off the wedding opinions/planning?
How do you stand up to my parents and still be respectful?