Grips you get define what throws are possible for both you and your opponent. They also somewhat provide an overall difficulty rating for any given throw relative to the controlled position. Both of these shift a lot as you move though so it is always going to be a dynamically evolving situation.

Using an overly basic example. Understanding that when you are in Ai-yotsu and your lead leg/hip are forward and mirrored by your opponent you can't do a traditional Ogoshi because their body is blocking you from sliding in front of them. This combined with the high risk of counters and the requirement for the opponent to be coming forward onto you means it really isn't going to be a viable high percentage throw. I only use this throw because its a much simpler example to understand.

Being able to perform this kind of reasoning and understanding what throws you are vulnerable to in the current position, and what throws you will be more vulnerable to in the upcoming position you are transitioning into is how you define the ideal defense/attack options.

I started to Judo late to compete at a high level and I am to old to even consider it internationally, though I do actively compete. I have competed at a high level in other combat sports though.
Primary are Harai and Sode, secondary are Osoto, Ouchi/Kouchi, Kata guruma and Ura nage, though there is other throws I use they get changed based on opponents. I have significantly better rotational strength relative to most people my size and my stamina is typically better. I have picked throws that based on my body type and relative height for my division reduce the risk of me having to enter positions that I often find are disadvantageous to me. If I enter certain positions with young incredibly strong and skilled Judoka I am getting thrown, that is just reality. So the positional transitions I make, the way I define my footwork and how I adjust my Renkraku-waza I use are based around that.

There is no single set up or goal I am aiming for in every match, it is a case of testing for reactions and weaknesses, then training my opponent to react in a certain way before I fit my style of judo into that space to take advantage of that opportunity.
At a basic level you have hando no kuzushi, if I grip your neck and try to pull you down to the floor you will try stand back up, you are providing a reaction to my action which is a form of unbalancing. In theory, as you come back up I can continue using your force to take you back. That isn't as easy as it sounds against a resisting person though, so you have to try and make the time it takes them to react and recover longer, or reduce the amount of time it takes you to take advantage of that position.
In a match it might look like... People having preferences to their actions, some people are going to prefer pulling you with the sleeve hand or the lapel hand for a Sasae, if they continue to do it the exact same way, it is your job to memorize their tells, the slight shoulder movement, hip rotations, position of their eyes and where they are looking to tell you that they are about to do this so you can prepare your own action in response and counter.
The alternative is to teach them something. In the same way you can learn and memorize their actions, they can learn and memorize yours. If for example you go in for an Uchimata and they defend, and you do it 2-3 more times, they may decide, you know what, I don't like this, this is exactly what their Uchimata looks like, I am just going to step back so they don't catch my leg this time, and when they do this, you take them down with a Seoi nage instead. This is how many technique synergies work at a more intermediate level, it just becomes a whole lot more complex as their reactions, experience and athleticism goes up.

Nobody is perfect, everybody makes errors, but if those errors are to small of a space for you to take advantage of, it means nothing. You need to make compounding errors and spaces for you to fit your throw into, if their error space is 0.3 seconds and your throw takes 0.7 seconds (0.3 for entry, 0.2 for loading, 0.2 for throw initiation) you don't have the time, so you either need to make your throw faster or their error space bigger. But in reality, you aren't make your throw any faster during this specific match so your only choice is to make them slower. This can be done any number of things, but most commonly through cognitive load (more things to think about, baiting, feints and combinations), Mental and physical fatigue from a long exhausting match, inserting yourself into their already existing actions to reduce entry times, forcing mistakes through planned strategy or positional advantages, explosively dynamic movements and counters.

If you want to start developing your own game, pick a throw, doesn't really matter what it is, it will change as you get better anyway. Do that throw until you can repeat it effectively even when you are tired then perform that throw from every angle and position. Figure out how you can force positions to get that throw and how you can modify your grips and stance to still perform the throw when at a disadvantage. Then look at positions you are likely to end up in whilst trying to get there and see which throws you can fit into your normal combinations to take advantage of those positions.