Is the car estimating how many miles you can get with a full battery based on the driving style since the last one or two charges?
No. Tesla cars don't display available range based on driving style. They use a constant to convert Wh to miles. For example, the Model 3 LR has 78,270 Wh usable capacity and 310 miles EPA rated range. That means the car will display 1 mi per 252 Wh in the battery. Let's assume the car estimates that the battery has 50,000 Wh energy. In a Model 3 LR in the US, it would display 50,000 Wh/ 252Wh/mi= 198 miles rated range. It doesn't matter whether the car has the small wheels or large wheels. It doesn't matter whether you have driven at 80 mph or 50 mph recently. It will still display 198 mi. There are a few things that can change this number. If you charge the car at night and come back in the morning, the displayed range will drop slightly because of vampire loss. If you switch the range mode setting in a Model S/X, the displayed range will increase instantly (usually by ~3 miles). There is no range mode in the Model 3. If the weather is too cold, the displayed range at 100% will be slightly lower.
Each model has a different constant. For example, the Model S 75D has 73,200 Wh usable capacity and 259 miles rated range. It will display 1 miles range per 282 Wh. Therefore a Model S 75D in the US that has 50,000 Wh energy will display 50,000 Wh/ 282Wh/mi= 177 miles rated range. In addition Teslas in Europe and Asia have different constants and different 100% range numbers.
The inconsistency happens because it is difficult to estimate how much energy the battery holds. The car is constantly calculating an estimate. It calculates how much energy goes in and out of the battery. But this is not an exact measure. It is not like measuring data on a hard drive. The energy in the battery is based on chemical reactions. These are affected by temperature and the vampire loss makes the estimates less accurate over time. Besides the balance sheet method, the car also uses voltage to estimate how much energy the battery holds. However, the voltage in lithium-ion batteries is flat until the battery is almost empty. Therefore this doesn't help much except you get a warning message that says power reduced when the battery is almost empty. Also, be aware that the accuracy of the displayed range will get worse over time if you never get close to 0% or 100%.