Lets start with your second question. If attackers run the same build you determine chain targets by goal. You have the option to take out big offense, split a kd nw, chose based on activity.... they'll all have the same numbers so its literally which prov poses the bigest threat to your kd and i get chose who i dont want big.
Next wildly different builds force the enemy to make the hard choices. lets say my top undead/warrior attacker has 35% GS, 20% hospitals 20% TG, 15 % stables, 10% Rax i put him on 1 tpa, 1.5 wpa 13 leet/acre 8 dspec/acre. What are your options to bring him down? NS/chain. Well hes my top atttacker its gonna take ALOT of ops to lower his off enough to make him stop hiting your t/ms i'll get in 3+ hits before your NS do any major damage. If u let him grow hes already accomplished his goal t/m damage DURING war who cares if u shell him out a little.
On the other hand if i had a larger- mid ranged attacker he'll be a prime target for NS since a few ops and he cant hit your unbreakbles and he becomes an easy shell. i'll probubly run high WT on that guy. maybe start war with 10% GS 20% WT.... use incoming land to up GS a bit as he becomes more and more likely a chain target. Then think about my mid-mid or mid low attackers. Whats the chance your gonna chain them or attempt to split my kds nw. probubly low if i have the right sized bigs. These guys are gonna grow. They should probubly have homes. WT/GS are meh on the to start war. i'd probubly start them with 15% homes. some banks, decent number of towers to feed chains runes. i'd start them with 10% TG too because as war continues i can up the TG on them and effectivly their offense wont shrink.
Its all about forcing your opponents choices. The ^^ assumes they act like every normal kd and chain big off, let the mid grow and then go after mid and if you do that i've countered you with my builds. if you DONT do that i had my kd setup such that im utterly crushing your t/m's, i'm massacring your mid...im overall making it so that your option to go after the people i didnt build to counter proves to be a bonus to me.