Well, I don’t blame you at all, especially if it’s really that bad with your current device.
My XA2 Plus is no speed demon either but I never considered it being particularly laggy.
But to come back to your original question, I can create a short video of the responsiveness of the UI once the Sailfish version for the 10 II has been released.
You should then be able to form your own opinion before investing any time and money in a new device.