Thank You.

What If I used 2 USBs (one for data and other for 0.5A) + 12V/1A power supply, will it suffice my need of 5V/0.75A + 12V/0.75V?

So unless your computer has charging ports, capable of delivering extra current

Mine is a Laptop but it’s adapter is 19V.

For the product you suggested, I’m looking for cheap products.