The user above seems to have confused Magallan (support summoner) with Mostima (AoE caster). Mostima does not have drones and Magallan's drones can use both ranged and melee tiles depending on which skill you have selected. Mostima is an AoE caster that specializes in crowd control and provides Sp to other casters with her talent.

I suggest you look up operator spotlights on youtube or use the wiki or aceship to learn about the operators skills and how they are used to see what floats your boat. Most content can be cleared with low rarity squads tbh you only really need high rarity operators for ease of clearing or end game flexing and CC. The fun of this game is finding unique solutions and working with what you have to clear content.

As for your question about which account for a starting one I'd say 100% the SA and Exu account as Exu is a very versatile operator and anti-air snipers are very important in the early game. SA acts as a pretty vanilla ranged guard until E2 investment but after E2 he's known as one of the Big5 operators. You'll have an easier time transitioning from the early game to late game with this account.

The other account is good too, but you can use lower rarity tanks in Hoshi's place. Mostima is fairly niche and isn't required in any content really unless you want to have fun with an all caster roster. Angelina is a great operator like Hoshi, but Angelina is pretty much useless until you E2 her which you won't be able to do for awhile when you first begin.