You can bulk unschedule and delete posts in Lately. The best place to bulk unschedule and delete selected posts is from your Content Library (Content --> Library). Within your Content Library, your posts are fundamentally organized by Campaign Tag name. Within the desired campaign, you can bulk select (check mark next to the posts on the lefthand side) the posts you'd like to delete. Once you've selected them, click the trashcan icon on the top lefthand corner of your library.
To make the process even faster, sort your Content Library by Status (ex: scheduled), Type (ex: Facebook), and Accounts (the desired pages). This will filter down to the range you're hoping to deleter quicker.
Unfortunately, we don't offer a bulk editing function in Lately. The best place to edit a select section of posts is in your Content Library (under Content -->Library). Here, you can use the filter options to filter by account (choose the desired accounts) status (ex: scheduled), and date range. This should hone in on the posts you need so that you can quickly jump into each post and edit accordingly.
To edit each post, click on the post itself in your Content Library. Once in the post detail page, click the edit post pencil icon to edit the post directly.