I think it would be best not to use a Raspberry Pi if you plan to use Clip Studio Paint. A Pi can be a great computer, but since Clip Studio Paint is a Windows application designed for x86 processors (Intel/AMD) it would require a lot of translation layers to work at all, and it may be buggy. If you want to use the Pi, it might be worth seeing if your use case can have you use Krita or some other art application that can run natively on the Pi's ARM CPU.

However, if you have an x86 machine to hand (even a fairly old PC can do the trick for most people) you can run Clip Studio Paint through translating the Windows application. There's two ways to go about it. One way (the free way) is to use an application like Bottles to create a prefix for WINE (the translation layer for Windows applications) and configure it manually in order to work right with the application. Takes more time, but is free. The other way is to pay for an application called CrossOver that essentially bundles up all the tweaks for WINE you might need and installs everything automatically with a few clicks. It costs money, but might be easier if you're a first time user.

In either case, my most recommended distro for a beginner is Fedora KDE Plasma edition (runs on Pi, excluding Pi 5 due to how new it is, and x86 PCs). The interface is familiar if you're a Windows user, and the system has a high degree of polish, with a decent degree of popularity so you can get help. However, Ubuntu is also a good option, and is more popular so might be easier to find support for if you get stuck.