For context, and regardless of limited airflow, temps under the hood of your car routinely reach 220F in the summer. In that area, there are many circuit boards, fuses, wires and electronic components (batteries, relays, alternators, etc.) that work just fine and last many years. An AFX3 in the average 70F room with proper humidity should be just fine. If a piece of gear has obvious slots in the case designed to disperse heat from multiple heatsinks, I will pay attention to that. In such cases you could simply and very easily (with the right tools- circular saw drill bit) cut out a notch or two in the case hence creating nice airflow that allows the heat to get out. Heat rises so be sure to plan your cut(s) not only at level but also slightly above. If it keeps you up at night, concern, simply buy a larger rack and add a 1u cooling rack but I think it is wholly unnecessary.
The chip and GPU are usually the biggest culprits for heat but again, I do not see this being an issue with the FX3- at all. Think of small laptops- they have almost no cooling vents and arguably they run more processing power and a large display. Playing HD videos and multiple monitor set-up will use a lot more CPU intensive than simply processing sound and a small built in display. Your amp/head and heat-sinks on your studio monitors do need good venting.
