I have a couple of 12" square soft boxes that slide over the end of speedlites, and a couple of the religious Nun shaped modifiers for my speedlites. I also have one of those 12" square speedlite modifiers that you can bend to shape. The soft boxes work sort-of OK if the flash is off camera, but tend to be in the way if used on camera. The Nun versions were included in several speedlite purchases and might help in inside crowded space work, but I have never used them. I think I've only used the soft boxes once and they didn't work all that well. I think they were mostly just not big enough to spread the soft light enough, but then I didn't have the time to experiment and just bounce flashed the speedlites off the white ceiling with the plastic diffusers on them. The 12" square shapeable speedlite reflector has worked best for me with the speedlite on camera and pointed mostly up but with a slight (30 deg) to get more noticeable catchlights in my subjects eyes, and for a little fill lighting. I have only used it a few times in probably a year and a half. So, for me, none of these have really been worth using, so far, but I'm doing most of my photography in my studio since COVID and I only rarely use my speedlites in the studio.
I guess I'm trying to say that I have several versions of these and have tried them on my speedlites a few times, but not enough to really develop a like or dislike for them. Maybe you should ask me this question again after COVID and after I have done more shooting using them.
Charley