If you own an iPhone 15 Pro or Pro Max there is an iOS 18.1 Developer Beta available that give users their first opportunity to try out Apple Intelligence.
I'm using every beta on my main devices, and all have been relatively stable for me since about beta 3. A couple of funky things have happened on iOS 18.1 beta, but it has been getting ironed out slowly but surely.
visionOS 2 beta has been great for me as well. No issues whatsoever, and it runs super smooth. Still waiting for the extended screen when mirroring Macs though!
Sequoia Beta 7 has been smooth as well.
I expect the betas released next week will be the RC (Release Candidate) for iOS 18!