Thank you so much for your advice! Would 12 units be too much?
No problem!

Short answer, definitely not! I did 12 units and it worked really well for me (well, technically I did 14 units, but I purposely didn't sit the HSC Exam for 2 units. It was a Retail Services traineeship through work, had no interest in actually counting it towards my HSC, just did it for the knowledge).
Long answer - If you feel like you are struggling with the work, handing in assessments late, that sort of stuff, then 12 units might be too much for
you in your current circumstances. It's a very personal decision to make. Just know that dropping a subject to go back to 10 units is
not a bad thing, and it isn't an admission of defeat. It's being strategic with your time!

But yeah, 12 units is definitely not too much, and it worked really well for me
This article could be worth a read! 