Preferred Deal Terms / Structuring Practices

Hi,

I have been learning about participating preferred stock in preparation for interviews. I am familiar with convertible preferred and participating preferred, but less familiar with "escalating participating preferred."

Does this mean that the seniority of the participating preferred escalates by fundraising round? 

Are there any resources / examples on how PE firms meet their IRR targets using these deal structures (convertible preferred and/or participating preferred) - that would be helpful! 

What types of situations a PE firm would target for a participating preferred in comparison to be okay with a convertible preferred?