That could definitely result in a smaller mah2 which may alleviate some of the memory strain. I would do that by renaming your existing mah2 (so as not to lose it if something isn't right) with Mango off, then starting clean and running the SQL restore.
The smaller the system, the more it makes sense to weight H2 above MySQL. But, if your database is large, MySQL and MariaDB are both very capable of handling it. H2 should be as well, and as I mentioned in the other thread there were some major improvements in the recent version of H2, which will be bundled in our next release.