No issues with its length, it coils up and I think I even put some velcro around it which gives it a nice handle of sorts. Mirror works good. Have to keep it absolutely clean and free of debris/dust.
It seemed as I was researching them, the choices for iOS were greatly fewer and less quality than Android/Google platforms. So if you are a Samsung/Android user, dip deeper than my recommendation.
Focus distance needs to be suitable for your usage - which based on your description I think you are ok.
At the end of the day, its really all about video quality. I was trying to find a bore scope - to use as a bore scope. Which means very small diameter but with a camera that is high fidelity enough to pick up very small imperfections in clean/dirty metal in extremely tight spaces.
What I realized is that there is a reason why high end borescopes are costly and its all about the image quality. I can tell you I have found a myriad of ways to use the item recommended above and for $35 or whatever it was, I've gotten my money's worth. So there's that.