I'd like to leave this concept of "options" out of this, because I feel it is a very vague and discredited "theory" that cropped up in Star City when writing up a new "theory" just for the hell of it was in vogue.
Under this "options" theory, Dromar's Charm is worlds more powerful than Mana Drain, which I think says a lot.

More options does not mean more power. The number of available options is an indicator for interactivity -- that does not mean that more interactivity is equal to more power! Dromar's Charm certainly offers more options than Mana Drain, and two of those options are interactive (life gain is definitely not). So yes, Dromar's Charm is more interactive than Mana Drain. But it is less powerful.
Interactivity and power are connected by one thing: If a player forces another player to interact and that player cannot, that is a very powerful play. That is what Androstanolone explained, and what also Mike Flores details in his article on interactivity (which I have finally read by now).
Also, this sounds like a direct spin-off "there are no wrong threats, only wrong answers". If you pose a threat and a player cannot deal with it, or deals with it wrongly, you are in an advantageous (sp?) position. This can be as simple as attacking when your opponent has no blockers, or as complex as playing Gifts Ungiven for Ancestral, Will, Tinker, Recoup. That is probably the most practical lesson that can be learned from the concept of interactivity:
Resolving any game situation depends on interactivity, because if you do not affect the opposite player or his cards, you will eventually lose. The exception to this rule are obviously combo decks, which give the other player no time to force interaction, or even to pose any threat. That is why it is so important to delay combo decks.
The best example here is Belcher. If you can stop the first two turns, Belcher rarely makes a comeback, because they have invested so many resources just to get Belcher into play. Force them to interact, e.g. by doing something against your first turn FoW, and they will lose. Belcher cannot interact apart from the Belcher itself, maybe a Draw-7 and SB'ed Xanthid Swarms. Note how the additional interaction through the Swarms can turn games around in favour of Belcher.
Most of the really good Vintage decks have become so streamlined that aside from Force of Will, they really have no good answers for resolved bombs.
[...] Rack and Ruin is how you cheat the race. Because it is the fastest thing you can do after he plays Trinisphere, and the most decisive, you should play more. Maindeck.
I included the Doc's pre-restriction recommendation because it illustrates how many players seemingly ignore that it is necessary to respond if someone forces you to interact. It mirrors forcefield's assessment. But do you really have to? I think yes, but you can also answer a threat with a threat of your own. Most threats are interactive by nature, and we know that, at least in Magic, a bigger threat better is the best answer.
So to take this tidbit to a conclusive point, you don't need an answer to a bomb if you have a bomb of your own. You only need answers to break a stand-off, simliar to the Cold War scenario:
Both sides threaten each other with atomic bombs. Neither has the capability of destroying the other's bombs completely to escape a retaliation strike. (Sounds kinda like a cluttered game of Magic, doesn't it?)
Now, if one side has a (working) missile defense system, it can win the war. But if it only has the defense system, but not the weapons itself, it cannot win the war but is likely to lose it. Why? Because the other side develops better weapons and missiles, which forces interaction: The defense system has to get more sophisticated -- and very fast, if it comes to the worst.
Whoever forces the interaction here is likely to win the war. Likewise, as I said before (and that is also the essence of Flores' article), he who forces interaction on the other player has a higher chance of winning IF that player does not handle that correctly. Sometimes, they will have the answer and turn the tables.
What it comes down to is: Can the practical application of the concept of interactivity be translated into "put the other guy into a situation he cannot handle"? If so, being more interactive is not the important skill but choosing the correct option is. And since higher interactivity equals more options, having an interactive deck gives you a higher chance of having the correct option available -- that's basically flexibility, which leads me on a related tangent...
...does that mean that Dromar's Charm is good now? Well, we always knew it looks good on paper. But it has a lot of restrictions on it that come from the game. The price we pay for that kind of flexibility is too high (uncastable and too high mana cost) to compete with less flexible, but more powerful cards. Also, Dromar's Charm has lots of options, but only one at a time can be used. That gives Dromar's Charm the
same level of interactivity as Mana Drain (or any other counter or removal spell). We see that flexibility is not equal to interactivity.
The question remains: Is the practical application of the concept of interactivity "put the other guy into a situation he cannot handle"?
Dozer