Yeah just Micky's focus is on the short term U21... maximising your players salary to make them a single position monster.
(more or less)
In your teams best interests, you want to have their salary rise slowly whilst boosting important skills.
so training them in outside skills whilst not boosting their primary stats as fast, will keep salaries down.
your players are perfect for inside focus SF's or really good PF's in the long term.
you should get the harder training done first while they're young, and for their height the hard stuff is OD, JR, guard stuff.
It's really up to you what you do.
you have 26k seats, there is really no need to build more in my opinion, but if you must then go for it.
you'll never need to build seats again.
i would suggest to look at your team, look at your opposition, and if you think you can maintain 6th spot or BETTER then don't buy anyone.
if having a bit more muscle is needed then you will need to hit the TL and buy what you think you need to fill weaknesses..
the benefits of NT players on your team is, they get more Experience from NT games, and you will also receive mad merchandise bonuses whenever they play for the NT.