I cannot answer for Japanese because I don’t speak it. I do speak a bit of Chinese but I’m still learning. Chinese uses pinyin (拼音) to input characters on a computer. That means that you “build” your characters by adding lines on top of each other to form the final character. You need to type on multiple keys to build one character. Pretty much like some European languages adding accents on plain letters by pressing the accent key and then the letter. Chinese is easy to use since some words are only one character or 2. I can compare pinyin system to old phones with ABC on 1, DEF on 2 etc. After it’s muscle memory like the rest. It takes time but once you get it, you can type very fast. It’s a very simplified explanation. Look into pinyin online to dig deeper if you want to As for the amount of characters used, I think it isn’t very relevant to think that way. As opposed to latin languages and their letters, characters have a meaning alone and grouped. Each character can be used more or less frequently depending of what you are doing or what is the topic you are writing about.

Again, I’m not a native speaker but languages is my job and passion. My colleagues from China explain it that way, but it might be very simplified. Im sorry if something isn’t 100% accurate or wrongly worded. Hope this helps

Edit: typo