How should I go about saving instances/models?

one way to save instances is: you store all component models in serverstorage and then make a list of how often, where, with what rotation, etc each model occurs. Like you say you basically write a script to turn all the information you need to recreate it into text (a table with string values), then save that text (table).

This is called serialization, and you can find some scripts online and in toolbox to get you started.

Of course you also need a seconds script to do the de-serialization: reading the text and recreating your instance from it, by cloning the models from serverstorage and placing/rotating them to the right spot.

You can save custom variables (like NumberValue) with this strategy too, or really save all the baseparts and their model structure so you don't need to save anything in serverstorage and all models can be completely custom. But keep in mind that the datastore has some limits on both string/datastore size and on how often you can make calls to it, so based on how efficiently your instance can be stored, it's limited in size if you want to save it.