Clarify solutions and add pros and cons section

Updated section headings to clarify proposed solutions and added pros and cons of the different solutions.

Author: noamr

css-view-transitions-2/two-phase-transition-explainer.md

@@ -38,7 +38,7 @@ The instant part of the transition can only use information knows to the old pag
 
 To achieve that, proposing two provide the following:
 
-## Allowing the author to control the commit scheduling
+## Solution 1: Allowing the author to control the commit scheduling
 
 ```js
 // Returns a boolean if the page is prerendered/BFCached and not render-blocked.
@@ -82,7 +82,7 @@ navigation.addEventListener("navigate", event => {
 - Only same-origin navigations without cross-origin redirects are deferrable.
 
 
-## Allowing animations to defer commit for a short period
+## Solution 2: Allowing animations to defer commit for a short period
 
 The above knobs can be very effective, but might also require expertise to get right.
 
@@ -94,7 +94,12 @@ The likely use case to let an animation continue till the end, so we can perhaps
 }
 ```
 
-## Security & Privacy Questionnaire
+## Pros and cons of the different solutions
+
+While deferring page swap provides full flexibility, it also needs care to avoid some footguns that can cause unwanted navigation delays.
+However, the current plan is to enable that first for power users, and take learnings from that experience into the higher level CSS-based solution.
+
+# Security & Privacy Questionnaire
 
 01.  What information does this feature expose,
      and for what purposes?