I like that there is a shield proficiency feat, but I think that one needs work. First off one of the features is being able to equip or unequip the shield as a free action which is the way everyone I've ever played with seems to play already. That dropping your shield requires an action seems to be about the most obscure and rarely enforced rule in the game, so ignoring it seems like a rather minor feature. Maybe this is an unfair criticism, but I've seen people make the same argument about drawing two weapons with the dual wielder feat, and I've played at tables that were relatively strict about one free object interaction, but I've never encountered a table strict about shields. Seems like it needs another feature.
More importantly though I just think, if making shields a spell focus is going to be one of the big selling points of the spell it needs a different name like "Shield Caster" or something, to make it clearer to the uninitiated browsing through that this is a feat for people who otherwise wouldn't be using shields to use shields rather than to make your fighter into Captain America.
I like that there is one for guns, though it might need some language to make it clear that the "loading" property is different than the "Reload" property, and generally would benefit from having an original feature. This feels like some cautious DM's homebrew reskinning of Crossbow Expert for a player who wanted to use a gun. Maybe it should make you proficient with gun maintenance and gunpowder production.
Otherwise I love them all. A lot of characters have been rescued from awkward multiclasses here.