Radiation exposure during micturition cysturethography (MCU)?

Hello, I'm scheduled for a urethrocystoscopy with MCU (micturition cysturethrography). I have a few questions:

1.) Most importantly: Can anyone seriously tell me how much radiation exposure I'd be exposed to during an X-ray? I can't find anything reliable about this online. Some say it's not as exciting for younger men and that alternative methods like MRIs are better. Others say it's no worse than flying three times. I still want to have children and am considering canceling the procedure.

2.) What I still don't understand: When the bladder is full, micturition occurs. Do I have to urinate with the catheter inserted, or is it removed for urination? Doesn't make much sense for me to have the catheter in? I've had that before during urodynamics. I almost couldn't manage it. You want to see on the X-ray whether there are any constrictions and whether everything is emptying properly? How am I supposed to do that with the catheter?

3.) I have problems with my pelvic floor and now have difficulty controlling erections, for example. During urodynamics, I got an erection after the anesthetic was injected. This didn't really go away and then became problematic. In the end, however, the catheter was inserted without any problems with a "half" erect penis. I didn't feel any pain or anything. So it seems to be working anyway. I'm afraid it will happen to me again. Hence the question: How many people are present at an MCU like this? Surely more than one? Just because of all the X-rays? Can this be discussed beforehand, and can one possibly be given medication to temporarily suppress the erection?

4.) Do you lie down during urination, or can you stand up?

5.) Are you completely naked down there, or do you get hospital panties with a hole?

Please don't make assumptions, only serious answers from people who know the process. Thank you!