People who have been away for ten or twenty years go on pilgrimage often, and the priests who hear confessions at the great shrines are used to them. That is the practical reason to choose a major shrine: confession is easy to find and anonymous. In Rome, St. Peter’s Basilica always has at least one English-speaking confessor, and St. John Lateran and St. Mary Major have English-speaking priests on most days. In Kraków, the Divine Mercy basilica hears confessions daily in English and other languages. Lourdes hears confessions every day at its own chapel in the sanctuary.
Each place speaks to a returning Catholic differently. Rome is the Church at full scale: the tomb of Peter, the great basilicas, and small neighborhood churches with an evening Mass. Assisi belongs to St. Francis, who started over in his twenties with nothing. At Łagiewniki, St. Faustina’s message of Divine Mercy was written for people who think they have gone too far, and the Hour of Mercy is prayed there every day at 3 p.m. Lourdes gathers the sick and those who care for them, and nobody there is asked for credentials.
You do not need to have everything sorted out before you go. Come as you are; the sorting out is part of what the days are for. If a spouse or friend who is not Catholic is traveling with you, they are welcome at every Mass and every shrine.