Regarding the Best Smartphone to Buy

I suggest you to go with the OnePlus 7 smartphone as first preference. The next choice definitely is Redmi K20 Pro. Both of them are powered by Qualcomm's Snapdragon 855 processor which is a top at the moment until the next SD855Plus processor / chipset which will come in a later date on different brand smartphones.

The other phones stated are nothing less but (lower processor and clock speed etc.) I am sure these two stated above will beat them in the current race unless otherwise.

Both the devices (OnePlus 7 and Redmi K20 Pro gadgets) have better camera and overall performances without any doubt. If you can invest little more then I can suggest you to go with even OnePlus 7 Pro smartphone as well.

Please check the below features about 5 products.

OnePlus7:
OnePlus is the latest addition to the ever growing line up of phones from OnePlus. It comes with a 6.41-inch Optic AMOLED screen at 1080 X 2340 pixels resolution with a notch.
Key specifications
Qualcomm SDM855 Snapdragon 855
128GB internal storage
Dual (48 MP + 5 MP ) rear & 16 MP selfie.
6 GB RAM
3700 mAH battery

Samsung Galaxy A70
The Samsung Galaxy A70 is being marketed as a multimedia powerhouse that can also deliver good photography results with its triple rear cameras and offer a smooth performance.
Display = 6.70 inch
processor = Qualcomm sanpdragon 675
Front camera = 32 MP
Rear Camera = 32MP + 8MP+5MP
RAM = 6 Gb
Storage= 128 GB
Battery Capacity =
4500 mAh
OS= Andriod 9 Pie

Samsung Galaxy M40:
The Samsung Galaxy M40 is a mid-range smartphone that comes with a metal frame at the back and 3D glass that tops the display.
The device has an amazing set of cameras and a huge storage capacity. Its powerful processor and long battery backup give its users a seamless performance. With the provided budget, it is one of the best handsets that consumers can have.

Xiaomi Redmi Note 7
It is a Pro smartphone that runs on Android v9.0 operating system. The phone is powered by Octa-Core 2 GHz, Dual-core Kryo 460 +1.7 GHz, Hexa Core, Kryo 460) Processor. It runs on the Qualcomm Snapdragon 675 Chipset. It has 4GB RAM AND 64GB internal storage.

Redmi K20 PRO:
Xiaomi entered the Indian market with a huge splash in 2014, selling its Mi 3 with the flagship Qualcomm Snapdragon 800 processor at an extremely low price.

Key specs
Display = 6.39 inch (1080*2340)
Processor=Qualcomm Snapdragon 855
Front camera = 20 MP
Rear Camera = 48 MP+ 8 MP+ 13 MP
RAM= 6 GB
Storage= 128 GB
Battery Capacity = 400 m Ah
OS= Andriod Pie