Disclaimer: have not played in a few years. So this answer is only true for a state of game from before the mistlands update (November/December 2022)
You will have a lot of chests with a lot of stuff. Inventory management is part of the game. You can not carry metal (heavy and important) through portals and are forced to transport them yourself. You will have limited inventory space. You will basically move through tiers of materials (woods, metals etc), but low tier materials will never be obsolete, so you need to store a lot.
That being said: it is all worth it. Your stuff can be destroyed you drop your stuff on death and it makes moving through dangerous parts of the map a lot more exciting and challenging.
sorry but no. maybe i am biased since my sole experience is driving the german autobahn, but i drive well beyond 200km/h on a regular basis, which i consider travel speed when the road is not too crowded. cars that could go faster than 250km/h are usually limited to 250km/h. traveling at that speed is loud and a bit stressful, since the difference between you and other cars traveling at lower speeds becomes too high. they will not see you coming before switching lanes and braking distances are very high. but cars dont randomly switch lanes unless tying to pass others cars and you can predict these situations and slow down.
you will not hover, you can control your car normally and the only required luck is to not have others actively try to kill themselfes. you dont need to be a professional race pilot and dont need special gear (of course cars can easily be underequipped for these speeds, but you dont need special gears.
do you mean speeds above 250km/h or speeds above 150mp/h? if that was just a typo i would argue a lot less because those speeds stop being fun to drive, but are also accessible for normal drivers with normal street cars (with enough power of course, but you see plenty of those cards on the average parking lot in front of any supermarket)