When summarizing long texts, it seems best to consider the know-how for summarizing long texts separately from the Japanese summarization performance of the model.
For Japanese summarization, you can find information by searching in Japanese, so you may want to refer to that as well.
As for model performance, it is a good idea to compare them using a leaderboard, but in reality, each model has its own quirks, so it is best to try out a few that seem promising.