What mods or configurations suit tall riders - over 6'/190cm? Do longer legs make a difference to the power dynamics of a bike? Can that be exploited?

In certain cases, some "experts" believe longer crank arms (i.e., 180mm or longer) are more fitting for use by taller / long-legged riders. It helps them make better use of their leverage, so to speak. Of course, this also makes it harder for those riders to "spin" while climbing and what-not, and other disagree that there is much, if any advantage once you get over 175 to 177.5mm cranks.

If you're talking about a club racing or competitive scenario, I think any rider 6'3" or taller may be at a disadvantage due solely to power-to-weight ratio. Unless you can get your weight below 180 (see Hincapie, George), you are going to be at a serious disadvantage on anything involving heavy climbing or a headwind situation. In the sprints, however, riders with more leverage can kick some butt, if their gearing, cranks, etc. is set up properly and they have proper technique.

Of course, I personally just go out and ride to be riding. This is just some stuff I've read and/or observed over the years. I'm barely over 6', and I refuse to ride in any competitive situation - for now. I just like to see new scenery and go fast downhill - generally yelling "Wheeee!"

i recall a story about the new owner of The Hour record. He's this 2 meter Czech guy. Many say he won it because he's so tall. In sprints you can get as low as you want, so wind isn't an outstanding factor. Also, in time trials, the key is to maintain a good average speed, and being fairly heavy is good for that.
But in any situation where you're out of the drops, being tall probably isn't so great.

Lennard Zinn is a proponent of bigger sized components/frames for taller riders. Is premise is that things should be proportionaly equal. He has done some testing of crank arm length for taller riders and found that they could benefit from crank lengths greater than 200mm. This is not an endorsment, just letting you know what I have read. He is also something like 6'8" tall, makes custom frames and cranks (from 130mm to 220mm), and has written several good maintenace books related to road and MTB cycling.

The one thing that WILL kill you are hills, everywhere else you can and will decimate anyone. If you have good flexibility, long legs and arms mean you can get into quite a tuck in the drops and have your body parallel to the ground very easily, which means you have almost the same aerodynamic profile as the others around you.

It is also mostly universally accepted that longer crankarms will help you. Currently saving up to get some 185mm TA's myself.

I have also found (this may be a freak occurence in myself) that having more muscle mass in my legs allow me to store more energy then tiny hill climbers. I can eat a good meal 2 hours before a ride, eat some ice cream, dehydrated fruits and salted crackers 20-25 mins before a ride and have some mean energy going on.

It's not about avoiding your weeknesses, it's about working with them, just remember that.

195 cm, all arms and legs, 78 kilos

Is it true that longer crankarms will help taller cyclists? I don't know what were are considering tall here, but I am 6'4".