Charging speed does drop as you get closer to the max of the battery. it is recommended you avoid going 100% in most cases to prolong the life of the battery. Sticking to 80% is what many manufacturers recommend. That last 20% in some vehicles can take a long time to complete. In normal use, a number of factors can affect charge time., air temp, battery temp, charging unit temp, etc.. I ran my e tron down to 4 miles of range and it took 45 minutes to get to 100%, that was my first road trip a week after getting the vehicle. Charge rate from 10 to 80% is 30 minutes, I was able to plug into a 350 kW, watch the speed ramp up from 75 to 150 kW after 10% to 80 then it slowed down to around 40 kW when it completed at 100%. After learning more about battery health, I charge to about 90% for long trips or 5% more that what is recommended by A Better Route Planner App, to give myself a buffer to reach the next charge point, in case I put my foot in it for a bit of fun.
Here in the US, ElectrifyAmerica is building out the nationwide network and their charge points for long distance travel and on a recent trip to a from California, the charge points were about 120 miles apart and I would end up with about 28 - 32% charge remaining when I arrived. I did have a bit of a hiccup as it was 117+ outside and the 150 kW charge units were not going above 43 kW, the 350 units got up to 120 kW and took a bit longer to complete the charge. These places had no canopy to shield the units or people from the heat. A big oversight in my opinion, especially in a state where the temps can soar that high in summer. The gas stations close by had one. In some places, I noticed large storage units that turns out to hold batteries. They charge those overnight when rates are low and can employ them during high peak times to reduce their cost. Most states the charge is 43 cents per kWh and if you pay a $4 monthly subscription, it drops it to 31 cents, some places are higher, this vary by state here.
While I prefer sporty driving, I would probably go for the GT Line instead of the GT to have more options and better range. We will have to wait and see how they price things here. I saw a review of the IONIQ 5 for the US yesterday and it seems like they will offer both batteries and do the same trim levels (SE, SEL and Limited) on both. I'm hoping they don't screw us and give us less sound deadening on these cars, like they do with their ICE vehicles in the past.