Why is it not listing the Lander and Happy Weekend fares when searching?
These fares will only show up for connections that are entirely by regional trains (RE,RB). Sometimes regional connections will show up on a "standard search", but often only express connections are shown because they are faster. To make sure you find these regional connections, change standard search to "only local transport".
The €27 Bayern-Ticket is available any day, but on weekdays it is limited to use after 9 AM. On weekend days it is valid from midnight (morning). On any day it is valid until 3 AM the following day.
Except for a few border stations (Salzburg, Kufstein, Reutte, Ulm) just outside Bavaria, the Bayern-Ticket is valid for any travel entirely within Bavaria, so there would be no need to use the more expensive (€35) Schönes-Wochenende-Ticket (Happy Weekend ticket) for that kind of travel. Only if your travel is going to take you well outside Bavaria into other German states do you need the S-W-T.
Click on "Purchase" to see what the "Savings offers" really are. The €29 offers are "Dauer-Spezial" fares which require use of an express train (ICE, IC, EC), at least a 3-day advance purchase, are limited in quantity, and are train specific (no "flexibility").
Are those lower prices even available without booking online?
The Länder tickets (such as the Bayern-Ticket) are not limited in quantity and do not require advance purchase. You can always buy them on the day of travel. Dauer-Spezial fares can be purchased at a counter for a €5 "personal service" fee, but they still must be purchased 3 days before travel and usually sell out before then.
The Bayern-Tickets ARE available. Last October I spent 2 weeks traveling around Bavaria, using Bayern-Tickets on five of the days. (For most of the rest of the time, point-point tickets were less than the Bayern-Ticket, so I used them.)
