My guess is that your heart rate and performance issues are from the Propranolo, a beta blocker, a class of drugs that restricts heart rate and can give you a feeling of being tired. I take Lisinopril with no side effects that I notice on performance. I also take carveidlol, which is a beta blocker, and it does have heart rate and fatigue issues for me. Over time, I have worked with my cardiologist to lower the beta blocker dose so that it has tolerable effects on heart rate/peformance, but it took a number of years and my doc starting to cycle before he agreed on lowering the dose. He also added a very small dose of amlodipine (2.5mg) when the beta blocker dose was lowered and we are both happy with my blood pressure. I ride about 6k a year and climb a reasonable amount. Sometimes, at my docs suggestion, when I anticipate a hard ride I delay the beta blocker dose until after the ride. This is usually on very hot days when the ride involves climbing.
My docs, present cardiologist excepted, have generally been deaf to the effects of beta blockers on my cycling activity. By far the most difficult issue is the limitation on heart rate when climbing or a faster group ride. My dose is such that I can peak out about 155-158 (I am 75) and on most rides I average about 115-120. Folks I am riding with, when I compare their Strava data, are in the 140 to 150 range, but then they are younger.
There are medications other than a beta blocker that might be more appropriate for your particular situation and bringing this to the attention of your cardiologist might present an opportunity for discussing options. If not, my experience is that over time it seems my body has adapted somewhat to the beta blockers, but keeping the dose as low as possible has made the most difference.