I have read that zero offset and flat lie angles cures OTT.
Which is the most important of these two?

If it is hard to find a club maker that can remove offset, is it ok to go with clubs with little offset
and get them really flat?
Or should I throw them away and look for a set with minimum offset?

It is true that both can significantly reduce the potential “left” pull vector. But to cure OTT, you also need to learn proper forearm rotation, and how to transition the club properly. ABS shows students how to do this with a very calculated methodology.

It’s not so much that the club specs will magically get trid of OTT tendencies, but properly set up equipment will make it easier to move in the right direction over time.

I guess module1 is a big key here. But for those who master mod1 how much “disaster” will the offset in modern blades do?
Most of the new blades are hard to “double bend” as the hosel is not long enough.

Most high end modern blades have almost no offset. My Mizuno MP68’s have very minimal offset.