I also use one of those Victron 275A switches, and at ~75A I haven’t noticed any significant heating. The connected cables are each 50mm². I measured it several times with an infrared camera under full load and once the temperature had stabilised, when the system was new.
When I bought the switch back then, there was also repeated talk of “cheap” copies. They look identical and are sometimes even sold as Victron products, but apparently the quality isn’t as good. Someone on this forum even did a comparison once and found some significant differences (if I find the post, I’ll link to it here).
Anyway, that’s why I wanted to ask: is it an original Victron product? Did it arrive in sealed blister packaging with the Victron logo?
Edit: I’ve found another post here where someone measured the different switches — the Victron switch wasn’t too bad.