Multihead with different GPUs

[Sargastic]

Hello,
I've been using a multihead setup for some years now, but only with my laptops (so, no dedicated GPU card).

I'm thinking about setting this up for several desktops. They will thus have an « integrated » HDMI port on the motherboard, coming from the (Intel) CPU, and a dedicated HDMI port from the graphic card (most probably Nvidia stuff). As far as I have read, this should work out-of-the-box but

• do you have any advice, especially as the graphic card is concerned (no need to have top-of-the-class graphics or performance) and driver (nvidia ? nouveau ?)
  
• Are there some weird caveats to avoid or tricks to perform for such a setup to work ?

Thanks.