Good question. I'm not in the best position to answer since that day was only the second time I tried sumo. The first was some months ago and that didn't go well, which is why I didn't try it again until my 'aha' moment.
So far, I'd say no, no issues in strength transition that I could feel. I mean, if I can get a five kg PR the second time I pull sumo there can't really be big issues in terms of strength transfer. That being said, I'm like you in that with conventional DL I do feel much stronger off the floor than mid-range. Just below the knee is where I usually start having to fight. Past the knee I can't think of any occasion where I've had issues at all. With the sumo I find getting off the floor is the hard part. I tried 230 kg after the 225 kg and I think I moved it about an inch, but I think I might also have been a bit tired by then. I'm hoping I'll hit 230 kg at the meet.
The thing is, I'm not so sure there is that big a difference between conventional and sumo across the board, and a lot of it has to do with anthropometry. I get this feeling that someone 'built to pull' (longer arms, etc) is going to be happy enough with either style and a lot is going to be determined by how you break off the floor which is going to be determined by where you are strong, if that makes sense.
For instance, when I initially tried sumo I think my biggest mistake was thinking it was very different to conventional in that I needed to break off the floor using my legs instead of my back by pulling my chest up - but that meant past about 140 kg I just couldn't move the bar. But, the moment I thought of initiating the pull the same way I do for a conventinal DL i.e. just standing up leading with my chest and not really doing much in terms of extending my knees at all I could move the bar very happily. The really funny thing was that coming off the floor between 150 kg and 190 kg felt almost identical, whereas with a conventional pull I really feel the difference in that range. Once I got to 200 kg, breaking off the floor started being noticeably harder than with a conventional stance but once the bar was moving it felt so much easier it isn't funny.
So, now I've managed to comprehensively not answer your question...
I reckon sntach grip and deficit snatch grip dead lifts are probably going to help you with sticking points more than changing stance or using sumo, simply because snatch grip is going to make the lift harder at all points not to mention all the benefits it provides in terms of upper back strength. I'm going to keep using it even while I do a cycle pulling sumo. You could even play around with paused front squats for isometric strength in your whole back. I think one thing with sumo vs conventional is that given how much harder it is to break off the floor you're going to need a back strong enough to ge the bar moving long enough for the leverages and hips to kick in; as opposed to conventional where I suspect you can get away with using your hammies, glutes AND back to start things off.
Does that make any sense?