Recently I am reading 走れメロス, and there is a sentence pattern that I am not familiar with (Group 2). Compare the following sentence groups:
There is a nominalizer の before the verb in Group 1's sentences, whereas it doesn't in Group 2's. I am aware that it is always plain verb followed by "がよい" in the text, but what does "plain-verb がよい"exactly mean? Does the meaning remain natural or the same if a nominalizer (say, の) is added? (Though I speculate "plain-verb がよい" approximates its volitional counterpart, but I am not sure).
Furthermore, can "plain-verb が" followed by other kinds of 述語 rather than "良い"? Is "plain-verb がよい" still used in modern Japanese? If so, would you use it personally in everyday life, hear it from other people's utterance, or the sentence pattern is more likely to be used in a play script spoken by actors?
It is my first time to see this sentence structure, so I have many doubts. Would you tell me as much as you know about this sentence pattern?