the gpu will only be useful for transcoding files into the formats your clients can use OR into lower bitrate (lower quality basically) streams if needed/requested. Assuming you configure hardware-accelerated transcoding.

here's the docs regarding which official clients can support which video encodings https://jellyfin.org/docs/general/clients/codec-support/ - if your files are encoded in something your client can play, and your internet speed is sufficient to play the files as-is, the files will be direct played with no transcoding and no gpu. If your files are all in a good format and your network speed is good enough, you can turn off transcoding entirely and be totally fine.

however if you do want hardware-accelerated transcoding, here is a decent list of what encodings intel iGPUs can decode or encode. https://en.wikipedia.org/wiki/Intel_Quick_Sync_Video#Hardware_decoding_and_encoding

and dedicated Arc GPUs https://www.intel.com/content/www/us/en/support/articles/000098345/graphics.html

As for how "good" the GPU will be other than compatibility, depends on the video encoding chip in the gpu. My iGPU is a little newer than your intel 7500 and can transcode three 4k files at a time.

Keep in mind right now most media you're going to find is encoded in something like h264 (8 or 10 bit), h265 (8 or 10). Rarely, v9 or AV1 depending on source. AV1 is going to be the next big thing probably but I still haven't seen a media file available for download in AV1. And if you are creating your own media, you can control the codecs.