Best upgrade path?

[rikona]

Currently running Ubuntu 16.04, and getting ready to upgrade. Will
likely go to Kubuntu - better for other family members, plus I run a
few KDE apps that don't play well with Ubuntu. I'm looking for the best
upgrade path. Seems like a new DVD install of Kubuntu would be best.
But, I have lots of data used by recoll, Shotwell, claws mail, etc. and
would like those programs to come up as they are now after a reinstall
of Kubuntu. Is ALL of that info certain to be in my home directory? I'm
assuming the new install will leave the existing home directory
structure as is - please let me know if this is not the case.

I have an EFI/GUID SSD with Ubuntu on it, home on a separate ext4 hard
disk, and additional large hard disks with lots of data. What do I have
to tell the Kubuntu installer to keep this disc arrangement intact with
the new install? Also, will Kubuntu overwrite any part of home, or just
add things to it that are needed by the new install? If it just adds
things, will the old stuff left in home foul up the new install?

I'm assuming I will have to reinstall recoll, Shotwell, claws mail,
etc. Recoll will likely need to be reindexed in the new install, as
might the others as well. Is it best to do some kind of app-specific
backup for each of these, and then recover using the backup after a new
install of each program? For Shotwell, I may need to use the existing
data files in order to preserve the tags and other info I've put in for
thousands of photos.

Sorry for the basic questions, but I'd like to do this in a way that
minimizes the possibility of foulups in switching to a new OS. And yes,
I will be doing a multiple backup before trying any of this. :-)) What
is the safest and most problem free way to proceed?

Thanks...