Our Post Grid Combo plugin will help you query posts by their tags. This article gives you a clear idea about how to query posts by their Tags.
Click on the Query Post Tab.

Now, by clicking the Choose button, you can search for tags. Here you will find some options; click your desired option.

For Tags:
The tags dropdown menu is accessible by selecting Tags. Next, type the Tag slug. According to the tag slug, your Post Grid will update.

For Tag ID:
Here type a Tag ID. The post grid will update with the specified tag posts.

For Tag And:
You can use this to display relevant posts to the entered tag ids.

For Tag In:
Here you can add multiple Tag IDs, which will update the Post Grid by showing those posts related to the Tag IDs.

For Tag Not In:
You can add multiple Tag IDs here, which will hide all related posts based on the tag ids.

For Tag Slug And:
You can use this to display relevant posts to the entered tag slugs.

For Tag Slug In:
Here you can add multiple Tag Slugs, which will update the Post Grid by showing those posts related to the Tag IDs.
