I have spacing issues on panels too, but I'm reluctant to file issues because my distro packages aren't the newest and I don't want to waste anyone's time.
But anyway for your case you might benefit from widening your vertical panel just enough to bump up the icon size, and/or forcing the task manager to use a certain number of columns.
I see a lot of good recommendations already, and want to add one more suggestion to try: Siduction.
I'm not sure how exactly its repos match up against the software you want more recent releases for but IMO it's worth checking in a live boot environment or VM.