i think the main point of these rule changes is to promote different drivers to do different things, kers is great because drivers can chose when to use it and it is quite equal, the tire situation is acceptable, but due to wear rate and speed difference, every1 just does the same thing, and marbles are bad for racing full stop.
as we see in the wet, why are wet races so good, its because that the track is slippery on the racing line and grip is else where, so every driver can take a different line as long as its not the racing line to get grip, and hence we see overtakes and some cars faster than others in some areas.
in terms of following a car, the problem as always been that the car in front will perform at higher percentage of downforce available to the car behind driving in turbulent air will cost you a few % of downforce and hence grip at the corners when cars are at the limit of traction the situation is unlikely to change as long as you have downforce, however, the problem has been the acceleration time to top speed, today's cars due to high power and gear rations accelerates almost in the entire straight and hence its hard to get a tow. if we reduce the power and increase drag to f1 cars, we will see that they hit top speed earlier and a tow is more available to the driver behind.
DRS is aimed to reduce such problem, however, as we can see in monza if the car in front is geared higher, your chances of tow is none. 1 obvious problem with DRS is the predictability, every driver in front knows when you are going to be faster and likely to over take and they will likely to know how the driver behind is going to do, hence as the season goes on, unless DRS gives a huge advantage, overtakes are well defend.
if care only have 500hp then i think there will be alot more tow available, given they design cars with the same amount of drag.