I have been using Clip Studio Paint Pro for a bit more than a year and recently upgraded to EX in the last sale they did, mostly because I'm also interested in doing animations.
I would say Clip Studio Pro is more than enough, the only thing I don't like about the Pro version is that you can't crop the image when exporting it. But you can just start with the Pro and upgrade anytime you want, preferably when it is on sale, to the EX version.
Also if you are getting a new tablet, depending on the one you get it is possible that it includes a license for Clip Studio (I think I got a 1 or 2 years license with my wacom tablet).
Since it's a software I use almost everyday, and the license is for life and not a subscription like others, I think it's worth it to get the EX. If I were you I would start with the Pro, which is more than enough to make a webcomic, then if you want you can always upgrade, preferably on sale, to the EX.