Yes as both emby and jellyfin currently use the same ports it might give an error when trying to use both. If you’re using docker you could run jellyfin on docker.
Apologies for the less than helpful response before, I have since spoken to some others in the community who have anecdotal evidence that jellyfin is faster when viewing images than emby was and I’m sure will only get faster as development continues.
If you’re just viewing the videos and photos on the same computer as they’re stored and it’s a desktop machine then using whatever file explorer you have would probably work well. For remote access you could use a samba share on your local network though that wouldn’t be useful outside of the network. Other than that I’m not sure of other software applications to suit your purpose but I’d imagine a Google might give some ideas