Greetings,
Welcome to the forum.
I am not a HP employee.
A single fan 1050 will fit.
I think you can do about a 10.5 inch dual slot graphics card in your chassis. You have to measure to verify this. Check the length along the PCIe x16 graphics card slot to see what you have. You need to be able to pop out an adjacent I/O backplate to install a dual slot graphics card.
You could do a better Nvidia card if you want. You may have to upgrade the PSU if you go to a 1070 (500 watt or better PSU plus one eight pin power supply dongle).
At some point the aging chipset and Intel processor becomes the bottleneck.
Don't consider upgrading the motherboard. (MB). This creates problems.
Buy a new PC if you want to upgrade the MB.
Regards