I would actually avoid silver tip tetras with gouramis personally. When I silver tips, I found them to be very nippy with the flowing fins on my angels. Of course, that can vary. but, I would personally skip silver tips and go with a different tetra. Black neons, neons, cardinals, pristella, penguin, and lemon tetras are a few commonly available tetras that pop to mind and would work fine IMO.
It is generally pretty hard to find female dwarf gouramis in a lot of places. The males are often a bit more colorful and sell better, so you see far more of them. For this reason, I would avoid them as a harem fish. The most commonly available gourami is the 3 spot gourami. It will be called the gold, blue, or opaline gourami. Either sex can be pretty temperamental and may or may not work as a harem in a community. Individuals can have highly variable personalities. I believe a harem of honey gourami could work out, but honestly, honeys stay quite small and I think a different fish might be more impressive in your tank. Though, its you tank. If you want to try a honey harem, you certainly can. If you just want 1 gourami, I would get whichever color of the 3 spot gourami hits your fancy. Personally, I like the opaline the best.
A few other schoolers to consider are cherry or gold barbs. They are not nippy like tiger barbs are, and can dwell in peaceful communities just fine. Also, rather than being strong shoalers, the males will compete for the females attention and herd them around a bit rather like guppies do. They are attractrive, and very fun to watch. I also find they fill out the middle of your tank well.
I have kept a good handful of different cories and loaches. I will say that I personally like loaches sooooo much better than cories. They are quite active, and pretty adorable. I don't really think that they would out compete cories as long as you feed sinking food, but your tank will look more cohesive if you pick just one species or the other.
Another fish I suggest is either a bristlenose pleco or a rubber lip pleco. They really don't efficiently clean your tank, and they poop a lot, but they are very cool fish to keep and pretty entertaining to watch.