Does this amount of units work in border cities as well?
Personally I don't think that's a good recommendation at all. The AI is going to walk all over you with that number of units for defence. It's not nearly enough and doesn't cover all the bases. You need at least one Spearman/Pikeman to counter any horse units a Civ might bring along or at the very least to destroy any that are happily pillaging your lands.
And he has no Bombard units at all in his lists. That's very important to have for a city's defence. If a big stack of enemy units comes by and parks itself right next to your city, you can severely blunt it's attack by going after it first and damaging a number of units with collateral damage. Also, if he/she has Catapults etc. and starts whiddling down your own defenders with them, your own Catapults are going to be immune to that damage and be at full strength when that Axemen etc. finally makes it's attack. I've lost a number of cities simply because I just didn't have enough bombard units inside of them. IMO, you can never have enough of those as they tend to die very quickly..
And he has no horse units! With the Flanking trait in BtS, one of the best ways to thin down a stack that has a lot of bombard units is to attack it with horse units. Having a couple of of them in each border city can go a long way to keeping your defences from being bombarded to almost nothing, and also provides you with a very mobile unit that can quickly reinforce neighbouring cities that might need some additional help.
His recommendation isn't even good for your interior cites, it's overkill for those. Two units each for those, of any kind, is more than enough. You only need to defend your border cities, your interior ones are pretty secure unless your perimeter falls. I've read a number posts where people mention that they don't even bother using upgraded units for their interior, they'll still have Longbowman in them when Tanks are out on the battlefield.
Also, I am trying to decide which trait is better: imp, agg, char, prot. Bottom line is I want to use a fin civ but I want a good army also.
It depends on what you want to do with your army, go on the offensive or just protect your own territory? I wouldn't bother with Imperialistic if you're concerned about your army though, it doesn't really do much for it overall. It's nice getting the extra Great Generals but they're not really going to have that big of an impact on your military campaigns. Charismatic is better but the two best are Aggressive and Protective, depending on your focus. Or you could just play the Japaneses and have both.