No you're probably right and that may be the reason I ended up with Komoot as it's the only phone app which does routing on the fly. I can't actually remember now.I could be totally wrong but I thought for RWGPS you had to use the web (PC) interface to plan routes and the app (phone) to follow them. The OP wants to be able to plan on the phone.
I'm a premium member and I have the app (but rarely use it), and the app (my version at least) doesn't do route planning.
But I have been repeatedly proven to be an idiot, so don't set too much stock by that.
Besides which I nearly always bow to the knowledge of people who say they could be wrong, it generally means they're not.