First of all, like all new formats, Hobby and Kiddy Pool are not in effect for a limited period of time, until we get a good grasp of the format.
Secondly, with the separate banlists there is a change in the Open Tier rules.
There are 3 rule sets under which Open Tier matches can be played:
TCG banlist with all the cards, OCG banlist with all the cards or TCG banlist with TCG cards.
There is generally not that much of an impact in TCG exclusives to go further than that, so mixed formats are fine. It should be noted that banlists are now made specifically for the available sets there, so current TCG banlist with Legacy of the Valiant is likely to get weird, therefore there is a TCG format available now. At the same time there is an OCG format available to play with that banlist. Be aware though that unfortunately DN does not support an OCG banlist function even in unrated, so for DN you'd have to go for unlimited to play OCG. YGOPro on the other hand supports both and can be used better for OCG banlist games. Be reminded that OCG banlist games being Open can still count for all Duel Achievements, so you may want to turn to them for some that the TCG banlist may have made harder (or impossible).
http://www.worldduelingacademy.com/t6701-wda-tiers#58363
