Alberto Knot is pretty good. Was my go-to knot for awhile for mono to braid/superline connection.
With practice you can tie it pretty quickly. When tied correctly it is quite strong and compact. Did have some issues with real light braid/mono with it and Fireline seemed to not like this not at times
Then again, I'm kinda anal rententive about my knots so might have been overly picky on it's failures.
Uni to uni is still probably the quickest connection knot IMHO. Slim beauty is pretty good too and basically what I use mainly now.
One of the strongest, but a little tricky to tie is a bimini twist in the braid followed by a yucatan knot for the actual mono connection. Beleive a few tests had this as one of the strongest possible.