Schlangers, TA, and Ner Yisroel are all excellent choices. You really can’t go wrong. I know boys who have come out of all three of them and they have good learning and good middos.
As far as how modern they each are, well, all are pretty yeshivish. I would actually say that based on the boys I know who graduated from each one, the most modern is Schlangers. I don’t think Schlangers is really as elite as periwinkle says. If your son is seriously interested, and if he has a strong learning background, he will be fine.
Ner Yisroel is really the default in Baltimore, though, except for people whose sons started at TA for elementary and middle school and decide to just keep them there, or those who have a particular interest in Schlangers.
Before everyone jumps on me for commenting on this thread, I grew up in Baltimore and I know these things based on my brother’s friends and my friends’ husbands and brothers.