No mystery about the theme this time. The clues themselves tell us all too directly that certain answers are anagrams related to other answers. A help for anagram solving, I find: Write out the consonants on one line and the vowels on a line below that one. Lightly put a line through the letters whose position you already know from solving crossing clues. This helps to see the letters out of their original context.
Tf you’re confident about the original, non-scrambled answer, any letters that show up in the anagram are likely to be wrong, so check those carefully. Notice particularly the unusual letters. Here G’s, B’s, Y’s and F’s show up.
27-Down – Galena and cerussite: What kind of things are “ite’s”? No, not like urbanites, these things come up from under the earth. 2 words.
87-Down – Like the word “curiae” in “amicus curiae”: Aren’t you sorry now that you didn’t take Latin? Or worse, aren’t you sorry that you did take it and still don’t know what “curiae” is. Well, I tell you what you don’t care about: the meaning is irrelevant.
88-Down – Was congenial: Like the clue, 2 words. The clue could be: What someone might have done after insulting their spouse.
26-Across – British soccer powerhouse: Or, where arms used to be kept.
14-Down Alters to allow development: Think towns, not maternity dresses
113-Across Video store penalty: And what makes streaming video so popular!
121-Across They’re on the left in Britain: Around the big cities, seems like left and right of these fit the answer. 2 words.
86-Down – Completely: Not a single word or even two. Similar to a common 4-letter answer to the same clue.