Sorry, I'm aware this is a very naive question, but I'm trying to get familiar with the tricky issues of new Google Analytics, and I'm not able to get them.

I want to start an A/B test with a section of my website, in order to change the web design and analyze the behaviour of the users through two metrics (the 'Average engagement time', and the percentage of clicks on the AdSense ads). The second metric would be the ratio between the count of two events: 'ad_click' and 'ad_impression'.

My strategy:
1) Create an event in Google Analytics, called 'MyWebTest'
2) For each one of the modifications ('A' or 'B'), assign a different value of the parameter called 'MyWebTest_modif'
3) Analyze/Compare the figures of 'MyWebTest', 'Average engagement time', 'ad_click' and 'ad_impression' on Google Analytics

What I did:

1) I created a custom event (through the 'Admin' section) called 'MyWebTest', with "event_name equals page_view" as Matching condition.

2) On my webpages, I inserted randomly:

gtag('event', 'MyWebTest', {'MyWebTest_modification': 'A'})

or

gtag('event', 'MyWebTest', {'MyWebTest_modification': 'B'})

(this is, I assign for the same parameter 'MyWebTest_modification', different values 'A' or 'B')

Under 'Reports > Engagements > Events' I can see the figures of the 'Event Count' of the event called 'MyWebTest'. However:
- I do not know how to browse the count of the occurences of the different values of the parameter 'MyWebTest_modification'
- I do not know how to compare the count of occurences of the event 'MyWebTest' (and the occurences of 'A' and 'B') with the count of occurences of the event 'ad_click'
- I do not know how to compare the count of occurences of the event 'MyWebTest' with the 'Average engagement time'

Perhaps my approach is wrong, and I would appreciate any help or similar experience. Thank you!