Switch from micro USB to USB c, buy adapters or new cables?
Personally I prefer cables without adapter. Especially when it comes to charging the adapter may reduce the maximum charging power (because it works like a resistor).

If you use an adapter I would strongly recommend to use an short adapter cable, not a small fixed adapter with a plug and a connector in a small case: The adapter without cable effectively extends the length of the plug and therefore also the force you apply onto the USB port on the phone's mainboard (because of the leverage effect). Hence using an adapter can decrease the lifetime of the USB-port.

Therefore I would replace the one or two most used cables for now. Others can still be used with adapter. In some months you know what you prefer and if it makes sense to buy more USB-C cables.