Need an advise for migrating to another device

General Discussion
1

Hello people,
I want to migrate some of my services (Pihole, Unbound, Letsencrypt / certbot, PiVPN) from my RPi 4 to a RPi 3 B+.
Which way would you recommend?

  1. Install EVERYTHING fresh and config new (the cleanest way, I guess)
  2. A complete fresh install of dietpi, install the desired software also fresh and only copy the configs to new device
  3. Install a fresh dietpi, then use a backup from the old device and delete the software I don’t want from the new device
  4. Clone/copy the whole current dietpi installation to another medium and just plug in into the RPi 3 (will this even work?)
2

Easiest way might be to simply plug SD card from RPi4 into 3B+. Usually system should boot ootb.

3

I would like to continue some services on the RPi 4.
But with your hint I will just clone the file system and copy it to another HDD, which I will use on RPi 3.
Thx!