Hi [NAME] thank you for sharing question.  Yes, it is safe to use laptop when charging on ac adapter power.  The battery icon in bottom RH corner should say Fully Charged (100%). The intelligent Dell battery profile will stop charging at Fully Charged (100%).  When only getting 70fps on just battery power, the Alienware m15 Ryzen Edition R5 laptop Battery (Removing/Installing) might require New Replacement OEM Battery. Dell Alienware m15 Ryzen Edition R5 OEM Original XPS 15 (9500) 6-Cell 86Wh Battery DP/N 69KF2, orDell Alienware m15 Ryzen Edition R5 OEM Original XPS 15 (9500) 3-Cell 56Wh Battery DP/N 8FCTC. When replacement battery arrives, check that year/month date beneath white label's square matrix is less than six months. If no white label and/or more than six months old battery it might be dead. This user advocates get extra purchase protection from Amazon, eBay, etc.   Please create windows Battery Report to confirm good battery charging performance. How to Get Your Windows 11 Battery Report (lifewire.com) or Windows 10 Battery Report: What It Is and How to Use It (lifewire.com).  
Is it ok to charge and play on my Alienware M15 R5 Ryzen Edition base model at 100%, because I'm worried that it will harm my battery? 
m15 R5, charging while playing