ACE2 (angiotensin converting enzyme 2) isn’t actually a “receptor” in its day-to-day role. Its job is to convert circulating, inactive angiotensinogen to angiotensin (which it does by cutting a piece off). Angiotensin goes on to bind completely different receptors to regulate blood pressure. The fact that SARS viruses settled on ACE2 as their primary target is simply an accident of evolution.
The mRNA vaccines trigger some of your cells to produce the spike protein in pretty much exactly the same way the virus does - except that the virus includes a whole bunch of other stuff that works to shut down all the other cell functions, forcing it to keep churning out viral proteins until it dies. With the vaccine, it’s all transient - some cells get the mRNA and dutifully produce spike protein for a while until the mRNA degrades. That’s then recognised by the immune system’s always-watching defence system as something new and foreign. If some of it does attach to other cells there’s no harm done - without the viral particle it’s just another protein. In fact, it has no way of getting truly “into” the cell (as in, into the cytoplasm) at all. It’ll just take a one-way trip straight to the lysosome to be broken down into its component amino acids and recycled as food.
Honestly, there’s no need to be making up scenarios to scare yourself.
