No, the Xiaomi Mi Mix 2 does not support 5G. The Xiaomi Mi Mix 2 is a bit old phone now and the 5G connectivity is not available even now.
So, you will have to wait to experience the 5G and will have to buy a new smartphone.
Check its full specifications Xiaomi Mi Mix 2
No, Mi Mix 2 doesn't support the wireless charging. Mi Mix 2 comes with a 3.0 Quick charging which will charge your phone really fast. The phone is having type C port which is Convertable and can be used from either direction.
For full specification check: Mi Mix 2
Samsung Galaxy S7 Edge vs Xiaomi Mi Max 2
Both the phones have their pros and cons, I think you should go for Galaxy S7 Edge. Galaxy S7 Edge has the following advantages over Mi Max 2 -
1. The Expandable Storage Capacity of Galaxy S7 Edge is 200GB while Mi Max 2 has 128GB Expandable Storage Capacity.
2. The display of Galaxy S7 Edge is 4K while Mi Max 2 has a Full HD screen, would matter when viewing high-quality movies or playing HD games.
It is not like that it is a one-sided game, Mi Max 2 has the following advantages -
1. The Display Size of Mi Max 2 is 6.4" while Galaxy S7 Edge has 5.5" Display Size.
Verdict - In my opinion, Galaxy S7 Edge is a better phone in overall performance but if you need a phone with good Display Size then, you can go for Mi Max 2.
You can also compare these devices on 91mobiles. Link - Samsung Galaxy S7 edge vs mi max 2