Sorry (later realized) I didn’t really answer your stocking query
This kit isn’t available in my country so I just looked quickly at online comments - some don’t like the filter as it’s open top and livestock kept leaping in
but perhaps this has changed?
Shrimp love to climb into nice cozy filters!
You can do a mix of tiger and cherry shrimp (mix of colours is fine re group population dynamic but try to do 8-10 individuals of each species), note that males usually remain significantly smaller than female shrimp
Generally a larger number of a single fish species looks “better” than fewer numbers of several species - and you will usually observe more complex behaviours
But it’s also fun to explore various species - they can behave/appear so differently in a home aquarium, especially with plants
If you pick up juvenile fish, it’s easy to add 10-20 in one go (I’m assuming stock will be limited to “small, slender” fish - deeper bodied fish are easily equivalent to 3-4 “small slenders”)
I’m also assuming plants will have established, with shrimp/snail added next, and finally fish - by then filter will easily cope with sudden fish introduction
especially if frequent water changes for a couple weeks thereafter
There are small fish which will thrive within the confines of a 60cm (long) aquarium, there are similar sized fish which need larger tanks to really thrive ...
Maybe list some species you like
Note that when adding new fish to established tanks, it’s alway possible to also introduce new pathogens, so keep an anti-parasite remedy on hand AND have done a water change the day before, then increased water change frequency for the next couple weeks (clean water is the best defence)