To quote from the web site:
The compact phase-change cooling system uses advanced thermal materials that quickly shift from solid to liquid for efficient heat dissipation. Paired with a large silent fan and three copper heat pipes, it delivers stable 60W performance, keeping your device cool and quiet whether you're working or gaming. The memory and storage also benefit from active cooling, reducing temperatures by 25% for better heat control and extended lifespan.
1. Any concerns with running it 24/7 ?
How hot does it get in the room where you intend to place the computer? If the temperatures are what most people call "comfortable" you should be OK. With commercial gear I assume an operating range of 0°C to +40°C ambient temperature. It may be different for some devices.
2. Does it consume less power than laptops?
The text mentions "60W performance" which implies it probably dissipates at least 60W when pushed hard. Some laptops come with 65W PSUs, others with 100W. Gaming laptops tend to use even more power. There is no "standard"power output for laptops. Some are more powerful than others.
You'd need to check what CPU is used in the UM760 and the CPU in any laptop you might be considering as an alternative. If both devices have similar or identical CPUs, they should use roughly the same amount of power.
Some laptops might well consume less power than the UM760, but their CPUs may not provide the same level of processing power. The package doesn't matter, i.e, square box or flat laptop. It's what's inside that's important.
3. Will it be able to transcode 4k and HDR content without overheating ?
Whether or not the UM760 can transcode 4K and HDR, depends on the GPU, if most of the decoding is handled by the graphics processor. What refresh rate are you intending to use? My 2017 OLED TV is only capable of displaying 4K HDMI content at 30Hz, which my GTX1650 media PC can handle. With a 60Hz TV, I might have a problem and dropped frames.
Regardless of whether the UM760 is capable of decoding your 4K video content, I would not expect the computer to overheat if it has been designed properly and you don't exceed the manufacturer's maximum ambient temperature operating limit.
The "large sllent cooling fan" means ite UM760 has active cooling, unlike the small NUC I use as a pfSense firewall. Yes, the CPU/GPU will get warm/hot when transcoding. The CPU/GPU might even reach thermal throttling temperature, e.g. 100°C, but the BIOS should "back off" the voltage to prevent even higher temperatures.
At room temperatures up to 30°C / 86°F I wouldn't be concerned. Above 35°C / 95°F, I might aim a desktop fan over the UM760. At over 40°C / 104°F room temperature, I'd stop using the computer. Just personal preference.
Please note I haven't checked the operating temperature range of the UM760, so you may have to modify your use of this computer, e.g if the maximum recommended ambient temperature is, say, 35°C / 86°F, or the minimum temperarure is 10°C / 50°F.
Try reading reviews for mention of transcoding performance.