1. Were the 'two to one' tactics necessitated by the existence of moderate dimensions?
2. Is any reasoning from the old wars with short ranges applicable to the present days of long ranges?
As regards the first, 'two to one,' though practised by Nelson, was certainly not invented by him. To overwhelm a part of the enemy with the whole of your own force has always been a principle of war, eternal because obvious. It is hard to find a period when it did not exist as the ideal objective. Alcibiades used it in the Peloponnesian war, and so has every winner since, and so will he go on doing till the end of time. But the 'two' (by which the superior force is meant) need not be a numerical superiority—it is a matter of indifference whether the superior power be made up of greater numbers of ships, superior skill in gunnery, superior courage, superior leadership, or superior anything else, so long as the sum of these things is superiority to the enemy.
Of all factors in war, superior gun-fire is one of the most important: to secure it—that is to say, to secure concentration of fire—those with the moderate-sized ships had, in the old days, to concentrate vessels.
Obviously it is begging the question to argue therefrom that moderate-sized ships gave victory—Trafalgar would have been won equally well with half the number of ships of double the power, or one third the number of ships of thrice the power, supposing such ships to have existed.