If youre looking for cross compatible support like on my game test, you should not use vehicle seat input at all. Some of the controls are terrible, specifically for mobile and console. The joystick, for example, controls both steer and throttle. The triggers also control throttle but the input is not analog. It is mostly better to map them yourself once you got basic input handling down. You can just use values for brake and throttle based on things like the fingers position or the triggers pressure. Steering is easy on console but complicated on mobile. I had to do a lot of rotational offsets and position based angles and also check if the fingers moving the camera have not been placed on a gui. Vehicle seats are great for beginners but if you want more input control and to make a more pleasing control setup for other platforms, custom input is the way to go.
On the topic of land vehicles theres 3 main ways you can design their movement:
These are vehicles controlled by BodyMovers, CFrame, Force constraints, and any combination of these. A notable example are the Jailbreak vehicles. Their drifting system is god awful (cars slide across the floor like butter) but they use these methods. Another example is the freemodel Jeep from the toolbox. It is a featured freemodel. These move by manipulating forces and torque in order to push a brick car along a path. The main takeaway is that the cars have really awkward handling and the wheels do not actually spin.
Rolling vehicles are a step up. They use rotational constraints to get the car moving. This is pretty obviously getting more advanced but more realistic. The vehicles start to act like cars and have a more dynamic friction setup. They control differently and handle differently but one of the easiest ways to make them is to use a couple of hinge constraints and a constant torque. These do not have any suspension but most likely have steering that doesnt just change wheel direction like the older roblox vehicleseat chassis. At this point you might have more physics problems such as vibrating or glitchy wheels. At this point you might also need to lower gravity, otherwise cars fall to the floor like theyre being shoved by a huge force. (btw dont use hinges for steering)
These types of vehicles are typically made up of 2 constraints: cylindricals and springs. Theyre definitely a step up from rolling vehicles but come with more problems like wheel clipping, suspension explosion (poor configuration), and they are pretty hard to get right. This might require even more lowering of gravity so that they bounce more realistically. JumpPower can be reduced and body forces might also be used to give characters proper gravity. These vehicles handle a lot better and also look a lot better. They can react to bumps, stairs, and terrain correctly. They get stuck less often and have better grip on the floor. The wheels are less commonly lifted from terrain at different elevations. They do wobble at low speeds sometimes though and I couldnt get suspension types like wishbone working well. (EDIT: you can make reliable wishbone suspension systems now!)
There is one more part to vehicle simulation however:
Engineering / Simulation
Depending on how you want the car to control and how you want it to act / react, there are different ways to apply these forces and velocities. From the very basic direct setting from throttle and steer to calculating realtime engine data scaled with car size and weight. Typically, everybody should start making crappy cars with terrible handling. It is easier to see your mistakes, learn, and get better from that experience. I am not saying you should not try, I am saying try to start simple. To learn actual vehicular engineering, you would need to study several sources on how engines, transmission, and powertrains/drivetrains work. After that, it is all about implementation and calculation. The topic of making vehicles is very generic. This would be similar to asking: how do I make art? There are many different ways to do it and many different methods for different situations and different people. Also if you wish to simulate things such as RPM and gear switching, you can do it the bad way by checking forward velocity or you can do it the actual way by checking slowest and fastest spinning wheel (in rolling direction).