S11 S21 interpretation when using square/ring resonator w/without enhanced coupling.

Here is "square ring" resonator, simplified without bends. Orthogonal feed for even operation. I can see some resonance at 12.7GHz

To decrease insert loss, enhanced coupling lines are proposed in few sources over internet. I add som lines:

Return loss (S11) is increased, i guess it is good, less radiation reflected back to filter.
What happened with insertion loss? Why it becomes bigger?
And also i cannot understand where is resonance frequency, i assume it can be found looking where return loss is bigger, and insertion loss is minimal. There are two peaks in S21, and ont peak in S11 graph.

And here is simple ring resonator:

looks even better than enhanced coupling square ring with enhanced feed lines... But from papers on internet i read about good sweet enhanced feed lines with pretty graphs.

Thanks!