About the FPS impact on contrails.
I run the quick tests in QMB (Ultrapack). 16xB-36D-III on Hawaii map.
Cockpit view, without FOV changes or "turning the head".
Average FPS:
5000 m ... 172 (no contrails)
7500 m ... 151 (contrails)
The impact is the most prominent when we see the contrails, of course.
In the same quick mission, when I use the external view and change it from 7-8 km (bomber formation is just visible) to about 0.5 km view, FPS drops from 190-200 to:
5000 m ... 120-130
7500 m ... 65-90 (the lowest when you fly into the contrail).
This is Ultrapack, which is very FPS friendly. And a simple QMB mission without additional objects.