With 'full-time' study the idea is that the classes + assessment requirements add up to full time. TAFE courses usually have more contact hours than Uni courses, and Uni courses usually require more out-of class reading. My last uni course was 2 contact hours per subject per week = 8 contact hours full time. It's the workload outside of the school hous that can be hard to manage.

Sometimes at uni you can be enrolled as 'full-time' but just select 3 subjects rather than 4 per semester, so it's a 3/4 workload.. I found that managable, but check with the uni if they allow it.