There are so many different oracles available that you are spoiled for choice.
I am going to look at them in broad categories.
The biggest of them all is Mythic. If you can learn mythic and it chimes with you, you can play anything and you probably won’t need another solo oracle, ever. You may want to add additional genre oracles, but everyone likes to have new things.
Other options in the generic group include Motif, which is gaining a lot of popularity, and classics like CGRE and FU [Freeform Universal] and MUNE.
System Specific Oracles
This is my own personal preference. The reason I like these is that if my game says to count the 6s to find the number of successes, then the oracle will also be based on counting the 6s to find your answer. If the system uses roll a d20 and high for success, the oracle will be rolling a d20, and high will be yes. Once you have grasped how the game works, asking if a filing cabinet is locked is no different from testing your security skill to pick the lock. Once you are in the flow you are just using the same mechanics.
If the system is dragon fighting fantasy, the prompts used for inspiration will often also be medieval or fantastic. If you are playing space opera then you may get some technobabble to keep you in the theme of the game. Something generic cannot do this final yard.
The whole topic of authoring and non-authoring is hazy. My definition of authoring has nothing to do with writing your journal. It references that every detail of your game, all those answers you create by interpreting the dice, come from your own imagination, just as all the world-building comes from the author of a novel. Non-authoring solo does not use or generate prompts that require interpretation. They are in the correct genre, and context and can be read literally. You get your answer, you read it [not interpret it] and then react to it.
This is an area where AI is becoming more popular, AI Dungeon is about the most sophisticated, but there are some very detailed pan, paper, and dice generators that can do this as well. My favorite approach is cut up oracles that involves taking the text from a novel and cutting it up into snippets of 4 to 8 words and then drawing snippets at random, then trying to sort them into sentences that answer your question. There is no interpretation involved, the words will be those of the author, and not dependent on your interpretation. There is a trade-off, as always, cut ups are slow at the table, but give a much richer experience.
The trade-off with AI Dungeon is that you need to train it to what you are looking for, and you tied to your computer while playing.
These techniques are certainly worth exploring even if they prove not to be what you are looking for.
These answer a specific question. You could have a book of 100 encounters to find in a forest. Then when your regular oracle or a wandering monster check says you have an encounter, rather than rolling for a wandering monster and then trying to imagine what is happening with your character and how to work the encounter in, you roll on your d100 table and you get a fully formed encounter. Some of these specialist tables can be very detailed and add a lot to your game. Over time you can accumulate a wealth of specialist tables to use as part of your gaming.
There is no right or wrong answer to which oracle will be right for you. As with everything solo, it all comes down to personal preference. It is a preference that is fun to find out what you like.