Report the tags conflict in your posts. Just put this script in the /scrips/ folder, and it would ran everytime the post being edited.

tags-conflict-reportor.js

hexo.extend.generator.register('posts', function(locals) {
  const tagMap = {};
  // first pass collect all tags in lower cases
  const posts = locals.posts;
  posts.forEach(post => {
    post.tags.forEach(({ name }) => {
      const lowercase = name.toLowerCase();
      if (!tagMap[lowercase]) tagMap[lowercase] = {};
      tagMap[lowercase][name] = (tagMap[lowercase][name] || 0) + 1;
    });
  });
  // second pass check all tags with cases conflict
  Object.values(tagMap).forEach(group => {
    const keys = Object.keys(group);
    if (keys.length > 1) {
      console.warn(`tags conflict: ${keys.join(', ')}`);
    }
  });
});