I tried to spam books (about 150), overall the TPS remained at 20, so I think the performance here is not bad.
for the server, of course, it would be better to use a plugin, but I think this datapack will also be a good solution.

1. in my original idea, the text actually should have been printed directly on the pages, not above the lectern. but I faced technical difficulties when trying to make the default text color black (like in the book). also, the text would be difficult to read, so I gave up this idea.
2. good idea. i will add it in next update.