Looks like I managed to solve my long lasting problem by just adding some thermal grease. I’m a bit buffled how big the difference is but all that glogging/jamming I had before seems to be gone. At least with the first test which is the PLA that caused me the biggest problems so far. This print isn’t perfect yet but that needs just a little bit of temp tuning I guess. Amazing to see that the new carriage seems to work better than I thought without the extrusion chaos.
Thanks for all your input guy. That motivated me enough to just add another few hours into testing and un/remounting the hotend.
For the upper end of the heat break, it doesn’t need to be anything special, normal CPU thermal paste is fine. For anything touching the heater block, you can use automotive anti-seize lubricant. The kind I use is good for several hundred degrees Celsius. I use a copper-based one that is rated for over 900˚C. Use it sparingly and run your initial warm-up in a well-ventilated area.