RTings is for the US market so TV model names listed there can sometimes differ from what they're called in NZ.

There is no good reason to use an OLED over an LCD in a basic monitor role. 

• Remains switched onto last HDMI each time its turned on

Most TVs will have a setting like "Start with last used input" to do this. If you're unsure look for the manual or ask to look at the TV's settings in the shop.

• No susceptible to screen burn as the screens get left on frequently

No OLEDs then because they don't like persistent static images. OLEDs can also burn in when turned off from strong direct sunlight.

• Decent picture in bright(ish) room

The strength of the backlight should matter there. Entry level models, often those with 50/60Hz panels versus 100/120Hz, will usually have weaker backlights. 

If you plan on using the TV's speakers, know the Chinese brands sold in NZ often have inferior speakers. They probably won't cope with being turned on alot either - same goes for Samsungs.