Is an 8gb sd card enough for hass.io in my case

I have a rpi4 with hassio doing home assistant things. It’s also running non automation add ons like portainer, sonarr, radarr docker, ad guard add on, samba. I was thinking of using my old 3b JUST for these addons. Would an 8gb sd card be enough?

Nope. A 32 GB or bigger card is recommended.

And, for that matter, an SD card doesn’t work well in a highly active (read and write) situation. Do a search on “SD card failure” and you’ll see what others have experienced.
You might want to consider an SSD.