can you, yes, but should you is the better question... its clearly worse with orals due to the blood pressure strain but injectables can cause bp strain to, think about tren for example...
Yes you can but I really am not a big stimulant guy. They do more harm then good IMO. If abused, they will raise cortisol levels and lead to adrenal fatigue.
If you want to use stimulants, just keep the use in moderation. A cup of coffee is no problem. A pot of coffee is a problem.