My current On shoes were purchased about 18 months ago, I think, so they're not recent enough to comment about the latest changes. The company does tweak things, though. They changed the last significantly between Pair 1 and Pair 2 in a way that made the shoes tighter over the arch. A few years later, they altered the material on the inside of the heel, at the top, and it wore out in the first week of use. They subsequently fixed that.
My feet are medium width, and I find the toe-box plenty roomy. It's hard to say about sizing since the shoes are made to the European standard, but I normally wear size 6-1/2 and my On shoes are labeled as equivalent to US size 7. That no doubt provides extra wiggle room for my toes.
I have a slightly higher than average arch. At the recommendation of folks at the shoe store that first introduced me to On shoes, I replace the original inner sole with an Aetrex 7700. That adds some arch support and extra cushioning, but it takes up a bit more space inside the shoe. This is an issue for me, especially with the waterproof shoes, because you can't do anything to loosen them across the arch; the tongue is solidly attached to the rest of the shoe. The shoes are completely comfortable for standing and walking, but extended sitting isn't good. For long train and bus rides (multiple hours) and certainly for transatlantic flights, I slip my feet partly out of the shoes to alleviate the tightness across the arch, which otherwise becomes somewhat painful.
If you're thinking the arch issue sounds beyond annoying, you are correct, but the shoes are so wonderfully cushiony for walking that I'm willing to put up with the arch situation. I've started using the original, thinner On inner soles for transatlantic flights, which makes quite a difference. I swap them out for the Aetrex inner soles my first night on the ground in Europe.
The tight arch makes the shoes a bit awkward to put on, so I sometimes travel with a lightweight, plastic shoehorn.