dl380-g7 is some really old stuff. 1st gen westmere. not very power efficient for the performance. there's no hardware encoding (qsv with encoding started with some 2nd gen).
how well it can do software encoding would depend on the cpu. but don't expect too much, and nothing more demanding than h264 avc at reasonable settings. you'd need a newer video card with hardware encoding for hevc, av1 or anything like that.
iirc there was a 6bay 3.5in option for those, and that cage/backplane might be available somewhere.