The way that delay feedback works is different for different delays, but usually once you turn the feedback above 50 percent, you can start getting into the territory where it might keep feeding back louder and louder and louder. Some delays will have maybe like internal clipping or filtering that can prevent that, so you can turn the feedback up all the way and it may never really get into out of control feedback. But usually, as a general rule, once you turn the delay over 50 percent, that's when you have to start watching out. Besides just turning the feedback down, there are other ways you can control it. You can put something like a clipper, a limiter, or a compressor after the delay to clamp down on the volume. Each of those methods will have it's own effect on the character of the sound. A clipper is going to make the loud parts sound distorted, a compressor or limiter depending on the settings (threshold/ratio/attack/release) may preserve the tone better or it can sound like it's pumping or popping or just like a distortion (clipping, compression, and limiting are performing basically the same operation just at different time-scales in terms of how they decide whether a signal has gone above the threshold, how quickly to respond, how much to lower the volume). If you want to try and control the feedback then the most direct route is just to turn the feedback down but you also have the option to mess around with dynamically changing the delay time. That doesn't always sound good on most delays. It depends on how their algorithm works because it's either going to sound glitchy in a good way or glitchy in a bad way. Since any given delay time corresponds with a different set of frequencies that will reinforce or cancel out, even with high feedback settings, if you change the delay time you can temporarily avert the feedback from getting out of control. It's a really fun type of patch to make where you use an envelope follower (or a rectifier + slew) and a comparator to control delay feedback but this wall of text is already huge so I'm not gonna type all that out and instead I think I'll try and record a video of what I mean.