Try watching the demo using that technique called the "Apple II 64k Cycle-counting Megademo" at https://www.youtube.com/watch?v=McKAcKVTIQs . There are not any artifacts with the changes between text and graphics mode in the middle of lines.
Later models you can bypass the floating bus/vapor lock and get VBLANK from a register (but IIe/IIc/IIgs all do it differently). I coincidentally released a 256 byte demoscene demo using this today: https://www.youtube.com/watch?v=iWq57yeu4gQ