Unit 1/2 checkpoints/other exam guides is probably a bit of an overkill. As for notes, if the 1/2 curriculum has a major overlap with units 3/4 (methods, economics, general English curriculum/skills guides-text study guides are unnecessary), having unit 3/4 notes is probably useful for a good foundation. If the unit 1/2 and 3/4 curriculums are very different, 1/2 notes are probably unnecessary. The main goal of unit 1/2 subjects is to do your best while focusing on your 3/4s, keep up with the work and build a solid foundation through understanding the key concepts (if the 1/2 curriculum is important for the 3/4).
This may be harsh, but completing 4 or 5 subjects in year 12 would be difficult for a person who is only prepared to study/put effort into 1 or 2 subjects in year 11.