There is one more test that we can do to collect more information, the test at https://www.youtube.com/watch?v=CjxjkDEE43s&t=723s was done using the lowest possible rate as you can see in the video, this took a lot of time , almost 6 minutes for the first replace to appear, perhaps by placing the highest available rate we can have a confirmation in the first 1 minutes, of course you cannot compare 0.004BTC with 6.6BTC, however we can have another result, so we would have to monitor exchange transactions 6.6BTC and see the average confirmation time and fees added to get a better idea of ​​what we can expect.