Do hybrids perform better than (Internal Combustion Engine) ICE cars on a long drive?

The battery and electric motors add weight, which requires more energy/fuel to accelerate up to speed and also adds some friction once that is done.

Regenerative braking means that most of that energy can be recovered into the battery when stopping and can be used to get the car back up to speed without using fuel.

But the longer you go and the fewer times you stop, the less efficient the hybrid will be, as once the battery is discharged it is just extra weight, you are not using its advantage.

For a plug-in hybrid this is more pronounced with a larger/heavier battery, but of course unlike hybrids with smaller batteries this allows electric-only driving for short to medium distances. If you can stop and charge at motorway services it should be a bit better than a "normal" hybrid.

The UK consumer magazine "which" got ~46mpg (which is around 20km/l) for a Prius for motorway driving. So you would have to take an average of that together with your other driving.

Others got 70+ mpg with a Hyundai Ioniq according to its trip counter.

They probably tried harder apart from going more slowly - typical Brits are racers.

I was really interested in the exceptional fuel average of hybrid cars and was considering to buy one as soon as I got my hands on some savings but I read somewhere that hybrids are better for city driving where you have to "stop and go" drive, they are not that efficient on long ranges.

What do you mean by "that efficient"? Certainly the Atkinson cycle as employed in most non-plug-in hybrids is very efficient in long ranges.

Not only that, but hybrids having a battery boost don't require an internal combustion engine for quick acceleration bursts. Rather the ICE is sized for its average load, and the quick acceleration bursts come from the battery. This also allows using the otherwise impractical Atkinson cycle which is far more efficient than the Otto cycle.

I would expect to gain at least 10% fuel economy benefit on long drives when comparing a gasoline non-plug-in hybrid to a gasoline non-hybrid car of similar size having similar acceleration.

Not only that, but the inherent automatic transmission of hybrids is very useful on all driving ranges, short and long. Traditional automatic transmissions often have poor efficiency, and the new technologies such as dual clutch transmissions have their problems. The single-speed planetary gearset of non-plug-in Toyota hybrids is cheaper than any other transmission can be, and you get continuously variable automatic transmission rations as well.

That said, there are manufacturers who take a gasoline car with huge engine and a really poor efficiency, lacking the planetary eCVT transmission, and put the option to charge the vehicle. Thanks to some of the ridiculous driving cycles employed today, they can advertise ridiculous figures like "1 liter / 100 km fuel consumption, 25 g CO₂ / km" although the car uses 10 times more fuel on long drives and emits 10 times as much CO₂ on long drives. On short drives if you always have the option for charging, such a car could achieve the stated figures, but no way on a long drive.

I don't have experience with non-Toyota hybrids but I can assure you that every Toyota hybrid you can buy, non-plug-in or plug-in, is very efficient on long drives.

Since I have at least 5 to 6 long drives greater than 500 km per year, my question is, that if they aren't efficient for long trips, then by what percentage does there mileage drop (In Km/hr please)?

Their mileage doesn't drop. At least for Toyota hybrids. In fact, a Toyota hybrid will have almost constant mileage all the time, no matter the environment (city or highway) or the speed. The only exceptions are that at really low speeds, efficiency increases and for really short trips where the engine doesn't have a chance to warm up, efficiency suffers. But for normal use you should see almost constant mileage all the time no matter what the conditions are. Compare this to a regular internal combustion engine non-hybrid car that suffers a lot when driving in the city.

And do they still provide somewhat better mileage than normal ICE cars?

Yes. For good hybrids, the mileage is always better no matter what the conditions are, if you compare it to a ICE car with similar size and similar acceleration.

An example of any toyota hybrid would be great.

My answer is all about Toyota hybrids. I have no experience with other brands.