UIC means don’t solve for the initial operating point. While it occasionally can get a simulation going, it does mean the initial solution is incorrect. You are basically required the solution to be incorrect.
“startup” was from LTspice. It was needed for many of the switcher models there. While it is a convenience in that you didn’t have to rewrite the input voltage as a PWL, it also generated some problems. QSPICE doesn’t recognize “startup.” Instead you have to rewrite any sources you want to ramp up as a PWL explicitly.
–Mike