When I was below 300, I was happy to hit the 700+ level players. They were worth so much gold. This is before they Nerfed the top players mana surge rates by almost 15%.
Kingdom bonuses make more of a difference than the level does in my opinion.
When they switched the kingdom bonus system, I only had 1 at level 10. Over the next month and a half, I leveled all the other to 10. With each kingdom I leveled, the gap closed.
The other gap I see, is some players in top guilds, had so many more traitstones available early, that troops with traits early made a huge difference.
So, to me anyway, the level doesn’t make a ton of difference. The kingdom levels, ascension, and traits had a far bigger impact on which teams are the most threatening.