The YouTube thing is Google's choice, not Apple's, as those are "premium" features. Install Vinegar (https://apps.apple.com/us/app/vinegar-tube-cleaner/id1591303...) to get a standard HTML5 player in YouTube, which will let you make it full screen, PiP it, background it, whatever.
I dislike the new Safari layout in iOS 26 too. https://support.apple.com/en-nz/guide/iphone/ipha9ffea1a3/io... -- change it from "compact" to "bottom". I assume this choice will disappear in the future, but for now, you can make it more familiar.
Unfortunately, I don't have any advice for the Clock/Alarm; I don't typically schedule one-off future alarms. That would be a useful feature.