Look into half height drives, they are about the length of really old CD-ROM drives while fitting into a single 5.25" bay. I would avoid the external drives, mostly because you find better deals on internal only SAS controllers and cables, and can use the other 3 channels on the cable for drives. External drives are nearly all Fibre Channel, which means optical cables.
I would not stick the drive in my main machine for 2 reasons: 1. I love the sound of the tape drive, but after the 2nd hour of non-stop servo motor sounds, it wears on you. 2. The SAS controllers and drives your going to be finding are old datacenter stock where energy use and heat output are an afterthought.
Make sure you can find the software to run LTFS on your drive. Even though there's really only 2 manufacturers of these drives, you cannot mix and match that software. For example, all the Quantum, IBM, and HPE drives are all the same, but will only work with each respective software suites. Firmware access is a pain in the ass, if you can even find it. I have an HPE drive, and had to dig out the latest firmware from one of their support DVD's for a ProLiant server, everything else wen't behind a paywall ever since HP split into multiple companies.
If your using Linux, you can fall back to plain old TAR and store data that way, but it's a giant pain in the ass keeping track of the data if you don't use some form of library software to keep track of everything, especially if your archives are huge.
I use mine mostly for full system images by using a NAS to copy to first, then onto tape so I have 3-2-1 backups.
LTFS is really nice, but if your dead set on using a GUI filemanager, you have to turn off thumbnails. I would stick with using the terminal or better yet, midnight commander for transferring data.
You can use the files directly off the tape with LTFS, video for example, set your player up with a large precache so it reads the whole file in, you don't want the drive to be seeking when you rewind a few seconds back.