I'm late to the party.
Acid Stream is meh.
Otherworldly Form is awesome for everyone who gets it, though certainly some classes get more out of it than others. I wonder if the spell level is right, though. Concentration certainly makes it a little limited.
Spirit Shroud I'm unsure about; I can't see Clerics using this over Spirit Guardians, maybe some Paladins will like it a bit more since they'll more consistently have a second attack, Eldritch Knights are probably getting the most benefit from this but they might still have better options.
The Summon spells overall are pretty nice. I think this is a much better route to take these types of spells than what was in the PHB. I used to maintain a guide on conjuring and when the ruling came out which removed player agency in the summon spells I didn't see much of a point in keeping it going. I like this direction much better. It also keeps away from the "wall of fur" which really was frustrating for some DMs to manage. I wonder if these only lasting an hour is good or annoying, though. They feel a bit like "pets" but they aren't pets that stick around. Maybe scaling the duration with spell level would help. Aside, if I use these as a player, I'm going to theme the conjurations from these spells to somehow be the same spirit that's changed somehow, with ditto eyes. I also don't think I like the 60' fly options.
The Summon Fey Spirit feels like it could be better, and it feels weird that you can summon an elf-looking spirit. I like how the "step" abilities work well enough. I find it odd that this is the only one of these spells that doesn't have a flying or ranged attack option. While Shadow Spirit also doesn't have a ranged or flying option, the abilities seem a bit stronger to make up for it (except Fear, which I think is bad, just because you're in dim light/darkness doesn't mean creatures can't see you so hidden kind of doesn't matter).
Summon Undead Spirit feels like a good frame to make a new Necromancer subclass with. Maybe allowing it to work similar to the variant ranger hunter's mark from a previous UA (some number of casts at basic level per day and no concentration, or maybe make it work like animate dead where they stick around longer). I much prefer this to animate dead and similar. Likewise, perhaps something similar could be used as a basis for a better beast master subclass.
The tattoos are all pretty cool but I'm not sure how I feel about their attunement stacking. At the least, I think there should be a limit to the number of tattoos in some way, maybe higher Charisma gives you the ability to hold more but I'm not sure I like that either. When originally reading this, I somehow managed to miss the section at the start of the tattoos that explained how they take up space. It works well enough that I feel my complaints aren't needed, except for: Illuminator's Tattoo, Masquerade Tattoo don't quite feel like they should take attunement at all. For the rest, attunement does make sense but still not sure about being able to stack all of these together.