SMS Number

Not directly. A number lives with one carrier at a time, and the TCR/10DLC registration you did in HighLevel is tied to that number on HighLevel's carrier (Twilio). RingCentral can only text from numbers that are on your RingCentral account, with their own TCR campaign registered through RingCentral.

So the two workable setups are: port the number into RingCentral and re-register the campaign here (budget a couple of weeks for the port plus TCR approval, and expect a short texting gap), or keep that number in HighLevel for texting and use a RingCentral number for calls, with something syncing the two so the conversation history isn't split. What you can't do is have both systems send from the same number at once.