Best Nilou Teams
Nilou is a character that makes the whole team identity revolve around the Bloom damage that she enables. This Bloom damage will depend on two factors: her own HP, and the Elemental Mastery of the character that triggers it. Since in AoE scenarios, the Bloom damage contribution relative to the whole team output can even reach 80-90% of the total, having the right amount of Elemental Application on the team (Bloom is an Elemental Reaction generated through Hydro and Dendro application= takes absolute precedence to the raw damage dealt by each specific character
These two teams are very typical variants of Nilou compositions. Aside from Nilou, Nahida is THE staple because of how consistent her Elemental Application is in AoE scenarios, and for how frequently she can trigger the Deepwood set Effects through her Elemental Skill
Other than this, in the first team Kokomi is used as the on-field character most of the time to generate consistent Hydro application. Since she's a healer, she opens up for quite the flexible 4th slot choice. Anybody can fit the role (preferably a Dendro character), but Collei and Kirara are my favorites there thanks to their quick-cast Dendro Application.
For the second team, Nahida is used as the On-Fielder as you're using a very good Off-Field Hydro applier like Xingqiu. In this case, since the team lacks a healer, the 4th slot needs to be reserved to somebody that can keep the team alive. Yao Yao is a great F2P option, but Kirara,Baizhu, Kaveh are also great of course
If you don't have Nahida, you're missing a unit that is irreplaceable at what she does, but a few other characters can act as Band aid. Generally, any Dendro unit that has Dendro Infused Normal Attacks can be an alternative to her On-fielder scenarios, so Al Haitham, Baizhu, Kaveh, all of these units are decent. It's worth mentioning that since you're lacking Nahida's consistency here, having a 2nd Dendro that can provide consistent Dendro throughout the rotation becomes more important (again Baizhu, or the upcoming Emilie).