In addition to minimum requirements from Rockstar for installing/running RDR2 on PC, here are some things to check/configure on your PC when setting up RedM:
Make sure your PC is up-to-date in regard to your Operating System, Steam and graphic card driver(s). If you don't know how to update these, head to Google with your system specs. (locate your system specs on Win 10 by clicking Start Menu > type "System Info")
Have at LEAST 10% free space on your system storage (AKA C-drive), and preferably 25% if you want to screenshot/capture (Again, head to Google for how to check C-drive free space).
How to add exclusions to Windows Security so RedM and/or Steam doesn't get blocked by the operating system.
Modify your antivirus for similar reasons as #3. Head to Google for how to modify your specific AV. Additionally, you can turn off your AV for initial launch and testing.
If you are using a PS4 controller and having issues with your PC recognizing it, use DS4 Windows for easy-peasy set up and usage! Pro Tip: Use Xbox controller for zero issues!
If RedM fails to launch and/or whenever RedM acts weird, quit all apps and reboot the PC. Then relaunch everything. Best practice is to reboot your PC before starting RedM...your PC and the game will thank you for it!
And speaking of rebooting, here's information about WHY restarting your PC is so important!