It depends on on copyright holders - some doesn't mind, some are overly sensitive about unofficial bootlegs.
I know I saw somewhere on the internet the list of artists/labels that holds their copyrights very tight - for example, it isn't a very good idea to remix ABBA, Michael Jackson and definitely not Beatles, they take it down immediately and very often leads to warning/instant deleting your SC account.
The trend that is now is if you value the number of followers on your SC account, you can create special account where you'll post only these remixes and bootlegs and then repost it by your main account so you still reach your followers with the your content. This will prevent (if some copyright violations are found) from deleting your profile with so hard-earned follower numbers, instead Soundcloud will erase only the account with copyright-violating content (aka bootleg profile)