Have you worked with compositions greater than 1080p?
Yes
Recently I worked with a composition of 3200 x 1280px
3200x1280 is only ~1.5 times the size of an HD comp so it shouldn't create huge performance issues.
-The temperature of the MBP rose too high, it reached a point where the touch bar stopped reacting
The new MBPs get really hot for sure!
-It had a blackmagic mini thunderbolt recorder in which I captured the switcher signal at 1080i
You're using the UltraStudio Mini Recorder not the UltraStudio HD Mini, correct? If so, are you using the Apple TB2>TB3 adapter?
the fps went down to 25fps every time I activated the bm recorder
with dxv videos the fps were normal 58-60fps
Is that a dip to 25fps and back up to 58-60fps or it stays constant at 25fps when you capture? Do you experience that when you only have the capture triggered?
What do you think is due?
Not sure. Can you describe your whole setup?
I've thought about buying an egpu (amd radeon pro duos or a wx7100)
What do you recommend me?
I run egpu's on Windows not Mac so you might want to talk to cvanhoose as I beleive he runs a 2080ti on a MBP.