With default font (Apple Color Emoji), the emoji in both preview and editor are misaligned and overlapping with the following text. The emoji behave normally when Apple Color Emoji in the variable --default-font is replaced with Segoe UI Emoji in custom css.
This is likely an upstream electron problem or something that apple changed recently.
If you have an old installer version you can try to download and install a fresh copy of obsidian from the website. Maybe it will help.