Hello @lpz87
The ram can be upgraded to a max of 64GB if you wish, so yes you can increase it to 32.
You should add matching memory though, to insure stability. Use a tool like Speccy to see what the timings are of the existing ram. Should be DDR4-2133.
You can upgrad to a 1080ti or a 2080ti. But do make sure whatever you go with, you find out the power requirements of it.
You will most likely have to change the power supply also. And take a tape measure and make sure you arent installing a card thats larger than what you have already. Make sure there is room to fit it.
You can upgrade the SSD also. You can replace the current sata SSD and/or you can add an NVMe M.2 SSD to the mobo.
Here are the specs.. .https://support.hp.com/us-en/product/omen-by-hp-870-000-desktop-pc-series/11084748/model/13378664/do...