Can we have visual encounters with angels on Earth?
Yes. Angels have interacted with humans throughout history. We see this especially in Scripture and in the lives of the saints. But it’s also important to keep in mind that not all encounters with angels are good. There are evil angels (devils or demons) who, according to St. Thomas Aquinas, can “work on man’s imagination and even on his corporeal senses, so that something seems otherwise that it is” (Summa Theologiae).
Then there are those in the New Age movement who promote angel encounters as a way into the spirit world where spiritual entities, disguised as good angels (2 Corinthians 11:14), are called upon to help us with improving our personal lives, etc.
Excerpt from the Vatican document—Jesus Christ, the Bearer of the Water of Life:
These spiritual entities are often invoked "non-religiously" to help in relaxation aimed at better decision-making and control of one's life and career. Fusion with some spirits who teach through particular people is another New Age experience claimed by people who refer to themselves as "mystics."
For more on this subject, I recommend the book Angels and Devils by Joan Carroll Cruz.