Path of upgrading from owncloud 8.1.5 to newest 9.x Version

We'd need to upgrade our owncloud server - now I have a question about the package repositories:
We're currently using the "old" one at opensuse:
https://software.opensuse.org/download/package?project=isv:ownCloud:community:8.1&package=owncloud

The Manual here:
https://doc.owncloud.org/server/8.1/admin_manual/maintenance/package_upgrade.html

sais that since 8.2 the new repository should be used

First Question:
How to do this in practice? Upgrade until the newest version which is availiable in the opensuse repo, then add the new open build repo and continue upgrading? Are there any knows issues on the way?

Second Question:
Why are there two repos?
CentOS_6_SCL_PHP54 owncloud-files-9.1.4-1
and
CentOS_6_SCL_PHP54 owncloud-9.1.4-2

Server configuration
Operating system: CentOS 6
Web server: Apache 2.4
Database: MySQL
PHP version:54 installed via SCL
ownCloud version (see ownCloud admin page): 8.1.5

regards
etraff

You might be interested in reading my experience at

which took me from 8.2.0 to 8.2.10 to 9.0.8 to 9.1.4

Your linked manual is exactly answering this question:

https://doc.owncloud.org/server/latest/admin_manual/maintenance/package_upgrade.html#upgrading-across-skipped-releases

The documentation at [1] explains the differences between "owncloud" and "owncloud-files".

[1] https://doc.owncloud.org/server/latest/admin_manual/installation/linux_installation.html

Yes thank you for pointing this out, I overlooked it!
So I don't have to delete any repos, just add the newer then? great!

About the Files/Not files version:
Which would be better for Upgrading? because v.8 had no "files" version - so is it safer to stick to the default version?