No, Samsung Galaxy A50 doesn't support wireless charging. To see the first look of this device:
To see the complete specifications of this device: Samsung Galaxy A50
Definitely, Samsung Galaxy A50 is not waterproof. Though it has a non-removable back cover, still it is not waterproof. It may sustain a few splashes of water, but it will not withstand a drop in water. IP67 or IP68 certification is not very easy to attain. All the ports, SIM stray, and speakers need to be water proof and ensure no water penetrates. You need to be careful while using your phone,if it drops in water, you definitely need to get a new one.
You can check the specs here: Samsung Galaxy A50
Service Center: Samsung Service
Yes, Samsung Galaxy A50 have a water drop notch and have screen protection too.
You can see detailed specs here: Samsung Galaxy A50
Oppo F11 will be a better option for gaming out of these two, as Oppo F11 Pro has 6GB Ram.
To see the full comparison of these devices: Samsung Galaxy A50 vs Oppo F11 Pro
OnePlus 6T is a lot expensive phone as compared to Samsung Galaxy A50. It has got high end features, elegant design and is true value for money. Samsung Galaxy A50 on the other hand, does have quality features at a great price. It will surely not let you down either.
Check out this interesting comparison by 91mobiles and decide which one suits your budget: OnePlus 6T vs Samsung Galaxy A50