Yeah, bidding can add lots of different variations to spice up the game. If you’ve ever seen some of SUD’s posts he’s given some in depth info on bidding styles somewhere in another post on bidding. But in general it all depends on how you want to play, i.e. RR or No RR. With RR, bids tend to be between 6-9, and with no RR they are 18+. So in a no RR game you could probably get at least 2 extra subs, but then again you have to be careful where you place them because Russia may take a shot at them.
Usually you don’t announce what you are buying or where you are placing the units until the bidding has concluded. However, there are certain styles of bidding where you announce what you’re bidding for before purchasing it. For example you bid 15, but announce that it is for a bomber for Germany. Your opponent may be willing to let you have it since he knows it is for a bom, but wouldn’t let you have it if he thought you’d buy 5 inf.
So, there is no set way, it just has to be something you and you opponent agree on.
The last part of you post describes a Stong Asia bid, 6-7 inf in Asia. There is also Stong Europe or Strong Africa. Played with no RR but a bid of around 20 or so and all units are placed in one region.
But most high bids get dispersed, 2 inf to Lib, 2-3 inf in Europe, maybe a couple in Asia. No right or wrong way, just depends on how you like to play.