Honestly, I've spent way too much time tinkering with these older Dell boards. The Intel Core i7-4790K 4.0GHz Processor is technically the best you can slot in there, but you gotta remember that the Q87 chipset in the 9020 doesn't support overclocking. You'll get the higher base clock, but you wont be able to push it any further. If you want a better bang-for-your-buck, check out the Intel Xeon E3-1271 v3 3.6GHz Processor. It performs almost exactly like an i7-4790 but it's usually way cheaper on the used market. Just make sure you have a dedicated graphics card since the Xeon doesnt have integrated graphics. Tbh tho, for Jedi Survivor, even the best 4th gen chip is gonna struggle. That game is a beast. If you do go for the upgrade, make sure your BIOS is updated to the latest version (A25 i think?) before you swap the chips or it might not post. Also, maybe grab some Arctic MX-4 Thermal Paste to keep those temps down because the stock Dell coolers are kinda tiny.

Upgrading the CPU in a Dell OptiPlex 9020 is tricky due to the motherboard limitations. The i7-4790K is a *slight* improvement over your i7-4770, but the performance gains for gaming, especially newer titles like Jedi: Survivor, will be minimal. Consider a GPU upgrade as a much more impactful improvement for gaming performance. Focus on a compatible GPU within your system's power and slot limitations.