-yes, i own 5 , 4 liquid and one 56 nitro
-regarding the saphire, only the nitro edition requires 3 8 pins connectors, the rest work with just 2
-even the nitro one, doesn't have a problem since you just need again 2 cables so not a big deal (for the third connection you can use one of the 2 cables  used anyway)
-regarding the performance, the liquid as said above, need a bit more power , but you could get over 2k on xmr easily with low temps, so might the card live a bit longer
-due to 56 being able to reach easily 1950-1980 , right now I would go all the way with the cheapest option that happen to be 56.
-other than price  just choose  any vendor since scarcity of vega doesn't leave enough room for vendor choice