no, yes, and no
1. Kuhli loaches grow to 4" long. A 14 gallon aquarium is too small to keep a kulhi loach in, and three in a 14 gal
would really be pushing it. Loaches also need LOTS of cover (hiding places) in the tank--caves, crevices, thick clumps of plants--and a sand substrate (rather than gravel) in order to really be happy & thrive.
2. Platys will be fine in a 14 gal
. Try to get 2 females & 1 male, or if you don't want babies, get 3 of the same sex. However, if you get 2 males and only 1 female, the males will harass her nonstop which will stress her out and likely lead to a very early death.
3. African Butterfly Fish grow to 4-5", which again is too small for a 14 gal
tank. They are also reasonably difficult fish to care for, as they tend to be finicky eaters, many will refuse to eat anything other than live food (small insects, live bloodworms, etc.)
Also if you are new to a hobby, a good rule of thumb for stocking fish is to research how large fish get at their full adult size, and then stock the tank so that as adults, you have approx. 1" of fish for each gallon of water.
So your suggested stocking plan would yield:
3 kuhli x 4" each = 12" of fish
3 platys x 2.5" each = 7.5" of fish
1 ABF x 5" each = 5"
TOTAL = 24.5" of fish in a 14 gal
tank... too much. While it is true with some experience and a very good filtration system you can push the bubble of the 1" per gallon rule some, it is not recommended that an inexperienced aquarist try that, especially not with a new tank setup.
In general I like the idea of your tank plan (a few bottom dwellers, a few mid-dwellers, and one surface dweller), I just think the particular ones you chose are not ideal for the size of your tank.
For a single showpiece top-dwelling fish (or mostly top-dwelling), perhaps you could consider a dwarf gourami. It is a common fish that any LFS
should have, comes in various colors ("neon blue" is the most commonly seen), and only grows to about 2" at full adult size. Another possibility would be a single male or female betta (fighting fish), which in my experience I have found to be very good "citizens" in community tanks. Your only concern would be, if you get a male, that there are no other colorful, long-finned fish in the tank that he might mistake for a rival male betta. But otherwise, a betta would be a nice addition too.
As for the bottom, it is a litle more complex as most bottom-dwellers are schooling fish yet you don't want to overcrowd. If you can find them in your pet store, you could try 5-6 pygmy corys or dwarf corys. If you can't find those, then maybe 3 or 4 of the smaller of the "regular" cory species (something like Leopard, Sterba, Adolfo's, etc. corys). If possible avoid the Bronze and Peppered corys, as they can grow larger than some of the other varieties I've mentioned. (BTW, sadly some aquarium stores will just lump together all of their corys in one tank and sell them as "cory catfish" without even knowing which varieties they have, so it can be tricky getting the variety you want if your LFS
isn't of the best quality). Another approach for a bottom-dwelling scavenger to help with "clean up" of extra food on the substrate would be to get one of the large, nice snails that pet stores often sell (apple snails, though they go under various other names including mystery snails), or a few ramshorn snails. If your tank has live plants you want to be sure you get a snail that won't munch on your plants, but if you have all plastic then that isn't a concern.
Good luck with your tank, and keep us posted on how you progress!