My Setup:
I originally was going to build my own PC, but I couldn't source all the parts I wanted in sufficient time. Instead I purchased an off-the-shelf Ryzen 5 3600 PC, with 16GB RAM, 500GB M2 SSD, GTX1650. When purchasing, I specified for 4 Video outputs, but on delivery the card only had 3 (1xHDMI, 2 DP). A bit disappointed, but for 3 monitors it's sufficient. I promised myself if I am successful I will upgrade. I also purchased 2 x 27" monitors, very basic, but get the job done. The top monitor is an old HP Compaq 22" that I had lying around.
I have a unique solution for the top monitor. I have some old TV mounts stuck into the wall (were there when I moved it), it's not compatible with anything I have. So I attached some thick wire to some screws in the back of the old monitor and 'hung' it on these old mounts. The desk can be adjusted to a standing desk (which I like to do around the time of the open), and then I move the top monitor to rest above these wall mounts leaning against the wall.