I'll touch on a few issues that stand out to me. Only thinking of the fish here.
Plan 1. The Hong Kong pleco, which is not a pleco but a hillstream loach, requires cool water (temperate, room temp max) and a strong current; fairly direct or bright light is necessary to promote algae which is a necessary food. These limit tankmates severely. Warm water tropicals are out, as are those preferring quieter water movement, or bright light. Most forest fish (tetra and other characins, rasbora, other catfish) would not do well in such conditions. Some possible tankmates would be some of the barbs, check those included in our fish profiles. The Hillstream Loach is also in the profiles.
Plan 2. The "pitbull pleco" is presumably Parotocinclus jumbo,
a species very closely related to Otocinclus. So it needs a very quiet tank, well planted, minimal water movement. The tetra are fine with this. And there is lots of room for many other fish. The water params are critical, as this fish will be wild caught and needs soft water with a slightly acidic to slightly basic pH, say 6.0 to low 7's max.
Plan 3 (first). All substrate, but given the species I don't see issues in a 55g. But upper fish would be advisable. Substrate fish frequently "hide" a lot with nothing above them, corys in particular.
Plan 4. You asked about tankmates for the angels. Several are possible, characins including tetra in the Rosy clade of Hyphessobrycon are usually good, just avoid a couple species that will nip fins. Hatchetfish, especially in this case the larger species in Gasteropelecus or Thoracocharax. Substrate fish that are small and peaceful, say corys. However, when spawning, this can be an issue. Substrate fish are usually nocturnal or semi-nocturnal, and will likely get the eggs or the fry at night.