Player bought Valda's Spire of Secrets; what do folks think of the spells and feats?

We're about halfway into what looks like a 4-year game. We started just before the big shift to 2024, so it's already a bit of a grab bag for my players with spells since it's like "are you a Legacy build or a 5.5e build" or whatever.

We recently learned that one of my players bought partnered content, Valda's Spire of Secrets. Because of sharing, that content is now in this campaign – meaning the 15 spells and the 4 feats. 

I'm not opposed, I just don't know this content or how balanced it might be in practice. This came up mainly with the spell "Dire Warning" and just what sort of structure would work well for that (getting us into a jank of time just talking about it at the table versus playing). Because I have a sorcerer, cleric, and druid PC, some of these spells can make their way into the game (daily, or on level up).

We play with a lot of homebrew rules and content, but until now have largely not had third-party content at the table. This is a resource-constrained, make-hard-choices campaign, and so in that spirit I'm adverse to things that seem like they're cheap cheats (not that I'm saying, or have any reason to think, the Valda content is). At the same time, I want my players to have fun and if they pick a feat like Iron Grip or queue up a spell like Polybrachia, I just want to be comfortable on my side of the screen knowing that this isn't about to become ridiculous (in the sense of trivializing challenges, not fun or funniness).

So! If anyone has played with this content, especially from a DM side, how'd it go?

I think I only have a problem with Iron Hero

Heroic Intervention. When an enemy you can see takes a Legendary Action, you can take a Reaction to intercede, preventing the Legendary Action from happening. You can take this Reaction a number of times equal to your Proficiency Bonus and regain all expended uses when you finish a Long Rest.

We use their stuff in a few games I’m in and it’s about average for third party content, some is too strong, some too weak and some just about right. One thing to bear in mind though is that a lot of it is obviously going for the punchline, theres lots of joke spells and things like the Muscle Wizard subclass has started with a joke and moved from there. Not a problem in a lot of campaigns but just the tone might be wrong of you’re trying to run a grim dark campaign