On your current phone (Android only), from WhatsApp main screen, click on 3 dots - top right corner- select settings, then chats and chat backup. Set your Google account as the address.
On the new phone, when setting up phone, do not add the Google account before setting up WhatsApp unless that's the only account. Start WhatsApp, enter number (must match number used in old phone), it will find the backup after confirming the device change with security code and ask for you to login with the Google account credentials. It will transfer all chats to your new phone.
You can also transfer using local backup on your old phone but that's more complicated if you don't know where to look for the files and it involves using a computer.
iPhone (iOS) only uses iCloud for backup so only Android will allow Google account backup.
1. Cloud storage - Google Drive 2. I will suggest not setting up WhatsApp/using it on new device without restoring chat history. It is more difficult to restore while using it. You can clear app data/cache to reset it if you started using it on new device 3. You need to download WhatsApp to new device but not using it. 4. Both need to have Wi-Fi or good data connection. LTE may not be ideal for the restore.
If you have reliable connection, you should be good. You may find YouTube video that will help you.
