As I mentioned, virtual end stops are nowhere near accurate. This is the trinamic system. It is using over current detection as an end stop.

This is a precision verses accuracy type of problem. If you haven't worked through these kinds of issues and ideas before it can be a struggle. Accuracy and precision are very very different things. All of our printers are precision; none of them are accurate.

Optical encoders are simple and cheap devices. You are likely limited to the shiternet's echo chambers when it comes to searching for information. There are a half dozen optical encoders built into most cheap inkjet printers. The system needed to locate each head on a printer is cheap, the tricky part is the software and designing the second head to be adjustable to match Z offset with changes like nozzles.

The main point is not tolerances; it is alignment. Alignment requires accuracy. Printers are cheap and simple because they are only precision machines. This is a fundamental design thing. If you want to build an accurate design, this needs to be engineered into every aspect of the machine from the beginning. This affects every aspect from hardware to software.