Thank you for all of this feedback! I think the best plan sounds like either a well-rolled Klein, an excellent 5* off-banner, or waiting for the 28th to see what the new banners are.
That last one depends on my luck. In the process of re-rolling but might give up for the night pretty soon.
I managed a double roll (did the first 10 or so quests) with Donnel + Shanna + Lon'qu + Mae, who are all A+ or above but aren't mentioned here. I assume there are plenty of A+ & S characters that aren't as beginner friendly? None of them were waifu material, so I trashed them anyways.
I'd also probably stick with someone like Lyn, Nowi or Camilla just because they seem reasonably powerful (especially Lyn) + I like the characters. Obviously same with Tharja.
Though as it is, most of my favorite FE characters seem not to be in the game yet (Nephenee, Say'ri, Severa etc) so that's sort of why I'd rather just roll for someone that makes the early grind incredibly easy.
Edit: Got neutral-natured Reinhart + Nino. Seems like a fairly reasonable start ^.^