Will my older pc handle wow midnight on decent settings?

Turn on the separate raid and battleground graphics settings. You can run nicer settings while questing and have it drop down automatically when you zone into a raid, which is exactly where an old CPU falls over. View distance is the setting that hurts most in cities, so that's the first one to lower.

what cpu is it? wow leans on the processor far more than most games, so an older gpu is usually fine and the cpu is what decides how it plays in cities and raids. questing solo is rarely the problem. the real test is a busy capital or a 20 person fight with effects everywhere. if it struggles there, drop view distance and spell density first, they give back the most frames for the least visual loss.