x3meblue, welcome to the forums. Rhivi, if you have RC installed on top of your store version you'll need to search for Procreate in the App Store or check your purchased apps list and download the update from there. Procreate won't be showing in the updates list for RC users.
As always you should make necessary backups before updating. It should install nicely over your RC and keep everything intact, but you can never be too careful.
Yes it requires iOS 11. Compatible devices are listed on Apple's page for example. If your device has iOS 11 installed it will run Procreate 4 too. Newer devices naturally will have more power and will perform better.
I assume you're using the cursed greyscale share icon when saving to Dropbox? It will mess up the filenames. The coloured icon used to work, but it seems to be changed somehow now. Can't get it to work at all.
Overall Dropbox's performance in the new iOS 11 isn't that great yet. They don't really take advantage of the Files app or drag and drop. Hoping they would update soon.
I dunno, the brush feels very similar to me in both versions. Can’t say if there’s any difference after a quick test. I’m using the first gen iPad Pro 12” and testing with the latest Procreate 3 and a beta of 4.
In your first example images it really looks like there are two different brushes but I can’t get that difference on my device. Have you tried importing the brush back to version 3 from version 4? If there’s something that happens during the export?
I personally like the real Pentel brush pen a lot and have been using it forever. It's been the main inspiration for my Procreate inking brushes. This Ukko brush is made to imitate the line of a slightly worn out old Pentel brush pen that has a soon to be empty ink cartridge in it. It will give the light lines a nice rough look while the heavy lines stay solid. This is basically like a forever half empty brush pen.
I've got updated versions of my other ink brushes too but I'll share those a bit later in my brush thread. Still need to make some final tweaks.