So, for judo in BJJ, there are some throws that may or may not “work/transfer over”… Sumi gaeshi being probably the closest possible thing to a “perfect” throw for Jiu Jitsu. Given the sometimes overly defensive BJJ posture of bent at the waist, that is used by some BJJ practitioners… This throw is sometimes quite easy to secure. The stance adopted in BJJ would rarely be allowed in judo in my humble opinion. Even if you miss the throw, you land in a safe open guard and can easily sweep from there. This is my second choice of throws when a match starts.
My first takedown attempt would probably be an ankle pick. It’s perfectly suited to BJJ because you can take and control the lapel and move uke easily. The bent over stance also helps to bring the foot forward by circling and can keep it planted by pressuring down on the lapel grip. This might be the highest percentage takedown.
From there, it would fall back to single leg and double leg takedowns. They both have their concerns in BJJ, but with a wrestling background, they can be changed to be fairly safe.
I’d stay away from a lot of the original judo throws. Uchi mata may be the most effective throw in Olympic level judo, but I’d never use it in BJJ given the stance and the fact that you don’t score ippon, you keep fighting in BJJ. So many of the other throws require uke to be much more upright than you will ever see in a BJJ match. Hip throws fall into this category.
Ippon seionage is often attempted in BJJ. It is a move taught early and often in BJJ. I’d avoid it given the stance, possibly drop seio, but you are purposely giving your back if you miss it.
Ultimately, it comes down to what you develop while learning as many techniques as possible. When you do find a move that works, then focus solely on it and learn every way to set it up and execute it. That is much more effective than trying to learn too many and not having a reliable one for matches.
An update for kata guruma, or fireman’s carry. This would be my best recommendation throw for judo competitions… Unfortunately Judo has changed their rules that make this move obsolete unfortunately. I do use it from time to time in BJJ, but it is not a dominant move when executed, it puts you in a slight scramble situation if the opponent leeches on to you.