The Heart Rhythm Society did a few randomized trials to assess the efficacy of calcium channel blockers, beta-blockers and digoxin in SVT. A comparison of verapamil, propranolol and digoxin showed equivalent efficacy in a small group of patients. However, in general calcium channel blockers and beta-blockers are preferred to digoxin. Digoxin has been around for a long time! I used Digoxin over 50 years ago for my PSVT, and my recollection was that it did little to prevent episodes. There are so many newer drugs now that are far more effective. My basic understanding of Digoxin is that it works on the heart's electrical system and decreases the heart rate, but increases each stroke volume. Wikipedia has an excellent article for Digoxin, and describes how it works very clearly. If it were me, I'd opt for a modern drug targeted for your type of SVT.
IV meds used to cardiovert can be quite uncomfortable I hear. I've never gone in to have that done. Mostly due to my ignorance years ago about my heart issues. I just laid in bed and cried until the heart kicked back to normal. That's no fun either.
As for which medication will help the best, it's unpredictable. Many people adore Verapamil and think it works great. I was on it for a week and ended up in ER due to some nasty side effects like chest pain and severe weakness and shortness of breath. However, I can take a different CCB (Diltiazem) without much trouble. Some people are on beta blockers for years and do well. I hate to say it but it kind of a drug roulette. All the doctor can do is have you try something and see if it helps you. If not, there are other choices out there.
Sorry you're not getting any replies, but your questions are rather patient dependent and specific. You doctor is you best source of an answer. I also comment I do not have any idea what "intravenous adenosine" is.