Fleet flyer wrote " I add 20/30 knots "above stall speed for landing and turns.
Thats a very sweeping statement !
If your aircraft stalls at 65 knts ( 1.3 stall ) = 84knts so +20knts would be OK for approach.
On the other hand in a Piper Cub or similar that stalls at 40 mph (35knts) at plus 20 kts you will float into the far hedge.
By the same token ,In the first example, if your 1G stall speed is 65 kts, you will need to be going much faster than 85kts to pull a 4g 90degree banked turn.