Nowadays, whether players use free styles or fixed forms, normally they should perfect creating chains when there's no fear of being under the enemy's sub-attacks.
Then again, most of the free styles which the then first-class players developed about 3 or 4 years ago are already treated as fixed form
s.Anyway, Creating chains regardless of the forms is to Puyo-pop what JUST combination technique to Fighting games.
Examples of fixed forms. GTR
(Gifu/Great Tanaka Rensa); One of very famous basements
Most players try to learn it after acquiring how to create more than 10 chains by stair/hook form.
GTR has referred to only this transition for quite a few years.SMR(Super Mimikaki Rensa. Other names;だぁ積み、丸め込み)
This basement is also famous.