The problem is with your Wi-fi router not being able to cover your whole house or penetrate walls, not with the Time fibre connection itself. If you use umobile 5G and it has a similar wifi performance, it will be the same.

Yes, that's why router can range from RM100 to more than RM2000. If there's no difference in signal strength, everyone would have bought the cheapest.

How big is your house in terms of square feet and do you have a layout image?

For reference, my old house was 750 sqft and a TP-Link AX20 router (rather old model) was able to cover the whole house even though it was placed near the edge of the house (a bit slow at the furthest room). Stock Unifi router back then couldn't reach the furthest room.

Now I moved to a larger unit with around 1200 sqft, I use a pair of mesh routers to cover the whole house (Main router in living room, 2nd unit in my master bedroom connected to the main via wireless backhaul).