Yes of following clearances in the manual, but no need for vents unless it says in the manual. The clearances are designed to stop it getting too hot and/or scorching surfaces around it. As said, it's room sealed so doesn't need any air for combustion, unlikely to need it for ventilation.. but I don't know the model specifics.
As for modern boilers all being noisy... not really. Not cheaply made unless you buy cheap. 10 years is about right for a decent one.. they will never last as long as a non-condensing boiler purely due to how they work. As for choosing a brand.. just by looking at a Worcester boiler (with the outer case removed) you can see how much better they are than most others. Vaillant are also similarly good. People are too bothered about the price that these better brands demand though, so they buy cheap rubbish that breaks down all the time and then complain that all modern boilers are "noisy horrible cheapily made pieces of tat that will last 10 years if your really really lucky and ten minutes if your not!"

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