I have 26.1 release candidate on my gen9. It’s better than 26.0, but continues to have inconsistent application of Liquid Glass “fog” at the top of Mail, Messages, and Safari, etc. I haven’t seen others mention this, but the text is larger than that of 18, which makes it feel crowded.
BTW, when I bought my mini gen7, it had 18.7. During setup mirroring another iPad, it insisted on upgrading to 26. I backed out, and started over as a new iPad. Then it let me update to 18.7.1. Finally, I reset it, wiping out all my information, and started the mirroring process again. Because it was on the latest version of 18, it didn’t force me to go to 26. I feel like I dodged a bullet.