You would never select Vref+20. The maximum wind additive is 15kts. When you fly Vref+15, that’s when Vref+20 (white bug) becomes the limit for the stabilized criteria. Check your manuals. I don’t think this is company SOPs and I’d be surprised if there was a difference there.
Even when you fly VREF ICE on one engine inoperative landings, your maximum wind additive is 5kts (so you’d be flying Vref15+10+5). I don’t think there’s a scenario where you would command an additive greater than 15kts for the current flap setting within the scopes of every checklist and Boeing manual. The only situation where a manual mentions a higher additive is for the speeds used in flap malfunction landings where speeds like VREF40+30 or VREF40+40 are mentioned. But in this case your flaps would not be F40 and the resulting airspeed becomes the effective VREF to which you should still add a 5 knot additive.
The only places where the manuals mention a higher additive is in flap malfunctions where speeds like VREF40+30 are mentioned but this is a different scenario, as you wouldn’t be using F40 (you have an assymetry) and the resulting airpseed becomes your Vref on which a minimum additive of 5kts is added.