I have a neurogenic bladder & bowel from a spinal cord injury in my late teens. Thankfully I liked diapers well before that.
I still have a lot of sensation down there. When I'm about to pee, I feel my bladder contract, and then a reflex spasm of my sphincter kicks in to hold things long enough for one to voluntarily take control. But because I can't voluntarily make that motor connection to hold any seal, it's only a few more seconds until I feel it relaxing from the initial reflex. This is when I feel urine flowing out of me, and while I can feel it all happening there's nothing I can do about it. I'm lucky that today's diapers are amazing and plentiful in quality that can easily hold four or five major wettings if needed.
Thankfully messing rarely happens, but when it did, it was a whole other ball game. At least when I pee in the diaper, I can probably go a few more wettings in public if need be before feeling like I should change so it doesn't start to smell like pee. But when I poo, it's like whatever I'm doing has to end now and I gotta go home and deal with it. Usually when my bowel is unpredictable like this, it's because I'm not feeling 100% well (constipation or diarrhea), so I typically pay attention to the signs hoping things will pass. Usually what I'll feel is a cramping kicking in unexpectedly during the day. I'm guessing 19 times out of 20 it's probably going to be gas and eventually my gut will settle down. But when it's not, I can feel this whole other level of urgency and activity within my abdomen start to take motion, and soon enough everything is coming out of me. I just can't do anything to stop it. Thankfully diapers can hold it in pretty well, but what they can't do is block the localized atmospheric destruction that takes place within about 20 feet of me lol. Over the years though I got good at recognizing when this was on the way and most of the time was able to scurry away from any public masses if it started at a store or even at work.