Controlled Group Compensation Question

[pholosofizer]

• Situation where 3 employers in a controlled group all have their own safe harbor match plan. 
• The formula is the same for all 3 plans.
• Definition of compensation will be different for one of them (not safe harbor definition - 414(s) comp ratio testing needed ... I'm going to refer to this as Plan 1), while Plans 2 and 3 just use 415 compensation.
• It's possible participants will be in multiple plans in any given year.

I've read/researched too much about it today and would like some input at this point as I might start overthinking everything. When it comes to 414(s) testing, a couple questions come to mind-

1) When running 414(s) testing for Plan 1, if there are any participants that were with one of the Plan 2 or 3 during the year, would those participants ratios be calculated using: Plan 1 eligible comp/All compensation earned from any employer in the group?

2) Would 414(s) testing be required for Plans 2 or 3 if there are any participants in either that also participated in Plan 1 (assuming their compensation from Plan 1 employer is not eligible in Plans 2/3)?  If all plans had the same definition of compensation, would this change anything?

3) Does being able to pass coverage separately (not requiring aggregation) change anything regarding 414(s) testing?  

Thanks for your help!