I started this way and eventually as I got more comfortable I went all in for plex media, and I've also lots of other files to the point where my server is just photos and personal docs. I'm gone from around 44TB in my array to only 16TB, where only around 4TB is permanent.
Re seeking, to be my mind it's got better since I started using rclone but it might be because I've got used to it now that I've gone all in. Have you tried experimenting with --buffer-size ?? I think a bigger buffer might help with forward seeking (not backward of course)