Whatapps - can. but make sure you have the latest backup on old phone on iCloud, then use the same number to set up WhatsApp on ur new phone. For first time setup, it will prompt u whether u want to restore from iCloud backup. Just make sure both phones are using the same Apple ID.
SMS - if u enable iMessage for the number on ur old phone, u should automatically see all the iMessages on ur new phone if u log in using the same Apple ID if iMessage is also enabled on ur new phone.
Then when u do the migration time, sms should have been backup and restore to new phone actually. (U should be able to verify it now)
Then the time after the migration, any new text messages (if not received as iMessages), only the old phone with the SIM card will receive, but u can enable text forwarding and forward it to ur new phone. With this new text messages after the migration will have it on ur new phone also.
Both of the above, make sure you have setup everything successfully on the new phone before you erase the old phone.
However, given the scenario u described, since you are not using the old phone, u will be better off to do one more time of new migration as new iPhone on ur new iPhone later while u are ‘ready’ to migrate to it to save all the hassle and retain anything that is possible on ur new iphone. Just erase the new iPhone and set it up as new iPhone u will be in prompted for migration again.
Dun forget other than text message or WhatsApp message etc., other thing such as in-app data if it is not iCloud enabled one will not be able to retain if u remain as what it is now and only use ur new iPhone later.
Such a great sharing from you.
Because I never think that I need to change SIM card until this weekend but I wanted to try a new iPhone like camera.
Noted, better to erase the new iPhone and migration again in order for me completely capture all the data.
Surely, will do... thanks again 😁