I am a current second year. My story is that I came from a solid university medicine residency and interviewed at mostly "mid-tier" academic centers for fellowship and could have stayed at my home program. I decided against staying mainly because I wanted to move to a city. I ended up ranking highly the one hybrid community/academic program that I interviewed at above many other academic programs because of location, more robust MCS and shock program, and the absence of interventional fellows which allowed general fellows a ton of autonomy in the lab. At the time I saw the latter as a plus, and fellows seemed to go to strong institutions for subspecialty fellowship. I was fairly sure that I was going into private practice so that factored into my rank list.
I ended up matching at that program and was quite disappointed early on. I wasn't prepared for how different the community setting is. Many of the medicine residents at my program are quite weak and require lot of handholding. There was less didactic teaching than I expected. We had less autonomy in certain clinical scenarios, particularly with MCS patients. One of the most disheartening issues was that one of the leaders in the division who is from a very well-known institution seemed to look down on us fellows because we are not at a big academic fellowship. Not having a home IC fellowship made the application process much more stressful. I underestimated the power of the fellowship brand in the job search, something I am still anxious about. All of this gave me imposter syndrome - will I be as strong a cardiologist as fellows from big universities? Will the name brand of my fellowship hold me back for the rest of my career? Am I doomed to be a second-rate citizen in the eyes of my colleagues?
The way to "cope" is to take advantage of the positives of your program. It's never as bad as it seems, and every program has positives and negatives. For me, I am allowed to do things that are reserved for interventional fellows at many programs. I ended up finding a strong interventional fellowship through my mentors. I have a close relationship with the cardiac surgery attendings and learn a ton from them which was not the case where I did residency. I will graduate with broad training in all major skills of general cardiology required for private practice. My co-fellows are excellent and have been able to find solid jobs in the area which is quite competitive. Some of my attendings are prior fellows and give me faith in how strong a cardiologist I can be.
From a competence perspective, understand that as long as your institution's clinical and procedural volume/diversity is not severely limited, you can become a very strong cardiologist as long as you are motivated and thorough. The most important factor IMO is that the patients and procedures are there for you to gain experience. The evidence base can be learned independently - and to be frank you should be thoroughly learning and reviewing the primary literature on your own regardless of where you train. Good clinical judgement can be a little more difficult because this is dependent on your attendings. Being at a place where the attendings are not all "experts," my approach early on in fellowship was to be aggressive about internally questioning the decisions and clinical reasoning of my attendings - corroborate their judgement with guidelines and evidence from your own reading. You will learn what each attending's strong suits are, when you can trust them blindly, whose technical skills to mimic, and when to not model your practice after theirs.
From a geography perspective, you may need to be more aggressive about making connections in the location you want to work in if your program does not have a strong national reputation or you are in a location that is undesirable for you. As far as the 3 years of fellowship, they go by fairly quickly. Living in a new location is always additional life experience in some sense. It may give you a new perspective.
Life will be fine. I still struggle with the imposter syndrome at times but less and less so every day. In hindsight I would have ranked some of the more well-known programs higher, and made sure to go to a place with an interventional fellowship. But nothing comes from dwelling in the past. There are idiots who come from great fellowships in great locations - go on Twitter for 1 day and you'll see. It is not the only determinant of your success and happiness.