I have some Helios 44 58mm f/2.0 lenses. Very capable of bokeh as you might expect but one of the properties of being a (slightly imperfect) Tessar formula lens is that the bokeh swirls around the edges.
The Pentacon 135mm f/2.8 has the nickname of Bokeh Monster, but is probably rather too extreme for video work.
The local Cancer Research charity shop had a batch of AA battery torches with a bank of LEDs down the side. I bought two, thinking that sometime, perhaps that extra bit of light might come in handy. £3 each.
Late to the party for mirrorless, Canon are still playing catchup.
It seems to be taking the centre of the sensor for the 4K rather than grouping sensor pixels together or evenly taking pixels across the sensor. I can do that as an option on my original model EOS-M in Magic Lantern by selecting Crop Mode as an option. That can be useful with adapted lenses like cine lenses that do not have an image circle that covers the whole sensor. That gives an extra 3x crop factor.
Plenty of spare batteries.
Vintage glass tends to flare much more due to less effective anti glare coatings so hoods can be more important.