Based on your search query, I would recommend Twee as it has a specific feature that aligns with your needs. The Vocabulary Builder feature in Twee allows you to generate vocabulary lists related to your teaching topic. This can be a great tool for creating vocabulary exercises for your students, such as fill-in-the-gap and open-the-brackets exercises.
In addition to this, Twee also offers other features that can aid in lesson planning and content creation. For instance, you can create multiple choice questions, open questions, and true/false statements quickly. You can also draft dialogues, stories, and articles for any level and on any topic.
The best part is that Twee currently offers free early access beta, making it a cost-effective solution for your needs.