I use the app Telegram for texting my Brother who lives in Europe, so the 4 siblings have Telegram installed on our phones, 2 use iPhone, and 2 use Android.
I have 3 phones I've bounced around using; iPhone 12 Pro Max, Pixel 4 XL, and Pixel 5a. I installed Telegram on all three phones, and even the phones just using WiFi connection no SIM card, they all show the latest texts and have all the chat history up to date, all the time. So switching between the three phones, my Telegram chats are all there just like on the other phones.
My iPhone 12 PM is my only Apple device, I don't own any other iOS devices, so couldn't tell you how that works. But no on RCS Google Messages, it only stays on the phone with your SIM card.
I have 3 phones I've bounced around using; iPhone 12 Pro Max, Pixel 4 XL, and Pixel 5a. I installed Telegram on all three phones, and even the phones just using WiFi connection no SIM card, they all show the latest texts and have all the chat history up to date, all the time. So switching between the three phones, my Telegram chats are all there just like on the other phones.
My iPhone 12 PM is my only Apple device, I don't own any other iOS devices, so couldn't tell you how that works. But no on RCS Google Messages, it only stays on the phone with your SIM card.