Do i need to hard wire from hub to desktop pc ? No
Do i need to hard wire from hub to tv to get sports ? No but is often better in order to get the best speeds
Is the wifi stable and do you notice a better signal than virginmedia ? Impossible to say. They all work to the same standards and can all be affected by interference.
Do you find you need repeaters around your hose to get a good signal all over ? Every property is different. Impossible to generalise
Welcome to this user forum.
Wireless coverage is likely to be the same, as all wireless routers transmit the same power, so you are unlikely to see much difference, unless the Virgin hub is really poor.
If coverage is poor, then extra hotspots (not wireless repeaters), are the answer.
BT will also allow you to use your own router if you want, so you are not forced to use the BT Smart hub.
Hard wired Ethernet connections or powerline adapter are preferable to wireless connections.
BT YouView can be hard wired, but BT can supply mini connectors to overcome that problem.