Question about Ubiquiti Amplifi Mesh Router

1. Ubiquiti is still improving the product with software updates. However, I would advise you to wait for Wi-Fi 6 systems unless the purchase is urgent. Practically all major manufacturers (Asus, Netgear, TP-Link) have announced Wi-Fi 6 systems (stand-alone and mesh) for Q4. Offering more is always relative. What is important to you? Good Wi-Fi coverage or extra features like network-level antivirus or similar? I live in a multi-storey old building built in 1911 and have tested various mesh systems. At the moment I've ended up with the TP-Link Deco M9 Plus, which spans three floors with a usable WLAN and offers an antivirus solution at network level. If you want a stand-alone router, the higher-priced devices from Netgear are recommended. By the way, there are already Wi-Fi 6 systems.
2 The stand-alone router is now supplied with a CH-compatible power supply unit. And if you still get an older system with a Schuko plug, Ubiquiti support will send you a suitable power supply free of charge. The situation is worse for the antenna modules, where Ubiquiti has still not managed to develop suitable adapters...

Thank you very much for your detailed answer. I appreciate your helpfulness very much. We live in a 4.5 room flat on one floor. The internet connection socket is in the home office at the edge of the flat. The Asus router is connected there to the Connect Box from UPC (500 subscription). A computer and a NAS are connected to the router via Ethernet cables. Two LAN connections lead from the router to a network socket and from there on to the living room, where our TV and an Android TV box are also connected to a socket. For streaming movies in 1080p from the NAS and for IPTV content from the provider Malimar.tv, we need a reliable and fast connection to the router. In the bedrooms furthest away from the router, the Wi-Fi signal is weak and barely sufficient for surfing the internet, let alone watching videos on the iPad. My plan is to replace the old router with a more powerful model with an additional access point with LAN ports in the living room. I am not a network expert who wants to optimise all possible parameters on the router. We are not gamers either. I only want to be able to assign fixed IP addresses for individual devices. User-friendliness and a device design that fits into the living room are important to me. The Ubiquiti AmpliFi seems to meet these requirements well. I find it a bit of a shame that it is not a tri-band device. Would you rather recommend a more powerful system because of the area of use described?