As per this link: https://ringcentral-faq.readthedocs.io/en/latest/sms/
"RingCentral's service sends individual messages up to 160 characters and can concatenate longer messages up to 1000 characters. "
Yes, big and long message require the receiving carrier to be able to process and combine the messages. and affect the carrier as it can take little time.
If you check this: https://developers.ringcentral.com/api-reference/SMS/createSMSMessage
There is a messageStatus in the API return:
Queued, Sent, Delivered, DeliveryFailed, SendingFailed, Received
You get to know the sms delivery status.
Also you can check the call logs