Thanks for the reply, I kinda forgot about this topic. Let me give a heads-up of where I am now with this.
I got a change to ask another person I know, who is also Chinese. She suggested Sogou when I showed the ones supported for fcitx listed on the arch wiki, so I installed that one by now. So far so good, but the minor won't start until February so I only use it for searching singular words atm anyways. I'm also only using the Pinyin version, not the wubi version.
I already had everything running for Japanese, so I only had to add the locals, install the language packs, font, etc. and choose which one to use. Getting the IME running wasn't an issue for me. Remembering how to switch between Chinese and Japanese unconsciously (where I used to just turn the IME of and on before so I have a different shortcut in my head) is the only thing atm . Just takes some time using it and I won't know any better anymore, I'm sure.
By now, I'm only wondering how to change the skin to a dark theme that will stay nicely in the task bar instead of showing buttons just above it as soon as I switch to Sogou. I decided to use the Mac skin for now that came with the package since it at least gives me a good dark theme in the input field. But the buttons still stay (with an ugly white background too) instead of just having the keyboard icon in my taskbar (which dissapears when sogou is on). However, the skin website doesn't load any images for me, so I can't see how the skins look, and I don't think they can be directly put into fcitx either?