@Twbr96 Devices will always connect to the strongest wifi signal which if they are physically closer to the booster will be that unit which will often be slower if its a "booster". A booster operates as a relay which can only deliver 50% of its connection bandwidth to the router - the other half is used for the backhaul traffic between the booster and the router.
If you really require higher speeds than 250Mb/s, which in practice is highly unlikely for 95% of business and leisure apps, then you need to change the booster for a mesh network solution ideally a triband system thst uses a third signal for backhaul activity. Sky's WiFi Max bundle is a triband system when the extenders Sky provide are in use but the extenders themselves are WiFi 5 devices so top out around 600Mb/s. You can buy multiple thitd party whole home wifi mesh systems if you prefer.
As pointed out above before spending money consider what if any apps beyond speedtests are impacted by your current speeds as few apps can use 100Mb/s let alone need higher speeds.
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65inch Sky Glass, 3 Sky Streaming Pucks, Sky Ultrafast + and Sky SR213(white Wifi Max hub) main Wifi from 3 TP-Link Deco M4 units in access point mode
