1-Handed and 2-Handed is basically a limit on weapons, shields and staves to equip. For example, Americo has a 2-handed sword, so he can't equip a shield or have another weapon in his inventory.
Meanwhile, 1-handed stuff allows to have off-hand equipment, examples in the game are Spear (1-handed) + Shield, Tome + Stave, 2 Staves, 2 swords and 2 axes (didn't get around implementing dual-wielding tough)
The boss weapons are effective against the blessings, following an elemental theme like you though :D You were on the right track. The secret idea, is part of the megaman inspiration for the map "kill boss-> use boss weapon" loop, it just wasn't executed that well on the current version :(
Each of the zone themes are original pieces by Forester, same with the title and ending theme. He also made the 16-bit player 1 remix. He is awemose like that, I will make sure to bother him about making the ost availible somewhere for people to enjoy it.
I cannot really say I have a preference of a starting zone, I tried to make each starting zone have a different feeling, but truly the only one with a strong gimmick is the Boar/Earth zone, because that one was the last one I made, also is the most consistant as a starting position even if the party is really limited healing wise. If you begin in another zone, the necromancers are actually a wildcard, because they can revive any mob from a previous zone.
The desert zone is actually another strong inital position, the bard's refresh works like FE4 so you can move pretty fast if you play with turn order and positioning, so it's not as bad as it seems at first.
Also, I love all my units, I just cannot pick favorites hahaha
Oh, I forgot to mention, Potions are meant for healing other people instead of yourself like vulnearies do, so they are the go to for parties with no healing. And the Angel Robe is bait for hoarders, because you need to kill everything and sell all boss weapons to get to 10k gold... is a dick move, I know.