Hi Lea,
if you have other painting apps, does the brush lag issue happen with them as well?
if yes, are you on the very latest wacom driver build released specifically for sonoma?
you might need to install it and reset all tablet preferences to default ones, because wacom drivers are quite complicated and can be buggy, particularly with the current mac os.
for anything artrage related you're experiencing right now, unfortunately you'll have to wait for the patch. you might want to get in touch with the team (support link provided above), but it really is about waiting for the work to be finished, since you can't roll back to an older mac os on a freshly purchased mac, apple does not allow that.