Are there any rules for when to use "appear to be" and when to use only "appear" followed by an adjective in English? Examples:
According to Collins COBUILD English Usage when used with adjectives:
Seem is usually followed by an adjective. If someone gives the impression of being happy, you can say that they seem happy. You can also say that they seem to be happy. There is no difference in meaning. Even minor problems seem important. You seem to be very interested. If the adjective is a non-gradable adjective such as alone or alive, you usually use seem to be. For example, you say 'He seemed to be alone'. You don't say 'He seemed alone'. She seemed to be asleep. In order to say who has an impression of someone or something, use seem followed by an adjective and the preposition to. He always seemed old to me. This idea seems ridiculous to most people.
Same for the appear. The two words follow the same patterns.
This said in your case there's no any difference in meaning.