I’d divide the lessons into:
- Kanji unlocked alongside radicals (those which are made from previous levels’ radicals)
- Kanji unlocked after Guru-ing radicals
- Vocab unlocked after Guri-ing kanji (unlocked alongside next level radicals)
Personally I like 4 the most. It feels good to learn vocab made of Kanji you just learnt before unlocking. I learn/memorize them the fastest as well.
For me, worst is 1 and 3. Since apart from the Kanji which takes after the meaning of identical radical counterparts, all of them require lots of logic and forcing you to recognize their meaning through mnemonics. 2 is better than these but suffers from the same problem as 3.
There is also 5. Radicals derived from a previous level Kanji, but they are probably the easiest out of the lot so I omitted them.