@very_rude_Turnip Welcome to the discussion!
Two questions about those voltages:
1)
searching for 1.8V FTDI on AliExpress generated no results.
2) If the serial port on the device side is already powered, you don't have to connect the Vc. Does it still matter whether your TTL2USB is set to 1.8V or 3.3V or 5V?