Changing mobile handset and network

[yorkshirelad1]

I've been waiting to get a new mobile phone and move provider.
I have had a Samsung Galaxy for about 8 years on an old EE/T-mobile SIM-only package and it's time to change phone and provider. Just seen the phone I want (Google Pixel 4) drop in price (been waiting for about 5 months) so pounced, and also ordered a giffgaff SIM.

So now I have the excitement of transfering settings, apps, data, contacts etc between handsets and also migrating my existing number from EE to giffgaff.

Any tips, gotchas, useful "do this before you migrate" ideas before I tumble down a well-trodden path of to-be-avoided pitfalls.
Any useful idiot-proof (for the technologically challenged) guides on the steps to take.

TIA!
YL

[Infrasonic]

I've got a Pixel 3a, great phone for the money.

As part of the upgrade process it could do a cable settings/apps/data transfer from my old Nexus 5, which if the battery on my Nexus 5 was better would probably have gone without a hitch (the Nexus 5 flaked out halfway through).

Whether you'll have that facility with an 8 year old Samsung I don't know, the big OEM brands tend to mess with the Android stock settings to suit their own ends (one reason I've always gone with vanilla Android phones like Nexus/Pixel).

I also have full sync and backups to Google Drive for all my Chrome browser, Android phone, Chromebook devices et al.
Recent versions of Android (10 is the latest) will back up far more to the cloud than before, which can be synced to new devices, but it still isn't a complete backup of everything.
Again what you can do from your Samsung is something you'd have to research.

For a complete backup/restore scenario you'd need something like Titanium...https://www.titaniumtrack.com/titanium-backup.html