Hi @Marketa Dobesova
Currently I'm driving a 2018 Jeep wrangler JL Sport trim, when I first got into off-roading I was generally surprised just how well the car performed, having said that I have since upgraded my car over time just based on preference however you can do all level drives with a stock Jeep.
So first of all, with features including front and rear locking differentials, an automatic sway bar disconnect, and a Rock-Trac transfer case, the Rubicon is the most capable off-road variant however this isn't really needed (someone please correct me if I'm wrong) but I believe that the Rubicon transfer case has a higher crawl ratio which just means more torque. More fundamental off-road equipment like skid plates, tow hooks, and hill start assist are available on the Sport and Sahara models and too are present on the Rubicon model.
When I first started looking at jeeps and their different trims it got confusing very fast, personally I would focus on trying to get a Sahara trim, because then you have the beauty of a sport trim with a little more comfort which if this car is also going to be a daily driver like mine it might be something to consider.
The Sahara comes with 18-inch wheels whereas the sport comes with 17-inch. Now how does this make a difference? you get a little more height to work with when using the Sahara for this same reason I changed my Sport wheels for Sahara ones, and they also look really nice too! Style points 😂
Now it is all about what you prefer, older model jeeps are awesome but also with older cars comes more investment if something were to go wrong, I've had friends with 2004 model jeeps needing to get the engine rebuilt due to underlying causes. If you're in the market for an older jeep be careful because previous owners could've done a range of "upgrades" which will cause issues further down the line so just watch for engine modifications or jeeps that may seem 'too good to be true'
Also, in the used car market look under the jeep it's common to spot bad rusting especially with older cars this usually occurs after taking the car to the beach and not getting an underbody wash to get rid of any salt that may have found its way onto the car's chassis.
Overall, the Rubicon is the most capable off-road trim, while the Sahara is the most luxurious and comfort-oriented trim. The Sport is the most basic and affordable trim, but still has off-road capabilities. It ultimately depends on your personal preferences and intended use for the vehicle.